Latex labels for Graphviz (work in progress)

build_graph.py

""" Latex labels for Graphviz """
import html
import re
import subprocess
from pylatexenc.latex2text import (
    LatexNodes2Text,
    MacroTextSpec,
    get_default_latex_context_db as get_default_l2t_context_db,
)
from pylatexenc.latexwalker import (
    LatexMacroNode,
    LatexEnvironmentNode,
    LatexWalker,
    get_default_latex_context_db as get_default_walker_context_db,
)
from pylatexenc.macrospec import EnvironmentSpec, MacroSpec

BLACKBOARD_MAP = {"Z": "ℤ", "N": "ℕ", "C": "ℂ", "R": "ℝ", "Q": "ℚ"}


def custom_mathbb(node, l2tobj):
    """ foobar """
    arg_nodes = getattr(
        node.nodeargd, "argnlist", getattr(node.nodeargd, "argnodelist", [])
    )
    arg = l2tobj.nodelist_to_text(arg_nodes)
    return BLACKBOARD_MAP.get(arg, arg)


EXTRA_WALKER_MACROS = [
    MacroSpec("textbf", "{"),
    MacroSpec("cong"),
    MacroSpec("mathbb", "{"),
    MacroSpec("text", "{"),
    MacroSpec("longrightarrow"),
    MacroSpec("Longrightarrow"),
    MacroSpec("iff"),
    MacroSpec("implies"),
    MacroSpec("sim"),
    MacroSpec("approx"),
    MacroSpec("equiv"),
    MacroSpec("lcm"),
    MacroSpec("lbr"),
    MacroSpec("bar", "{"),
    MacroSpec("vspace", "{"),
    MacroSpec("ord"),
    MacroSpec("gcd"),
    MacroSpec("mod"),
]

walker_ctx = get_default_walker_context_db()
walker_ctx.add_context_category(
    "math-extra", macros=EXTRA_WALKER_MACROS, prepend=True
)
walker_ctx.add_context_category(
    "env-extra", environments=[EnvironmentSpec("cases")], prepend=True
)

l2t_ctx = get_default_l2t_context_db()
l2t_ctx.add_context_category(
    "math-extra-override",
    macros=[
        MacroTextSpec("textbf", "@@@BOLDSTART@@@%(1)s@@@BOLDEND@@@"),
        MacroTextSpec("cong", " ≅ "),
        MacroTextSpec("mathbb", custom_mathbb),
        MacroTextSpec("text", "%(1)s"),
        MacroTextSpec("vert", "|"),
        MacroTextSpec("longrightarrow", "⟶"),
        MacroTextSpec("Longrightarrow", "⟹"),
        MacroTextSpec("iff", "⇔ "),
        MacroTextSpec("implies", "⇒"),
        MacroTextSpec("sim", "~"),
        MacroTextSpec("approx", "≈"),
        MacroTextSpec("equiv", "≡"),
        MacroTextSpec("Z", "ℤ"),
        MacroTextSpec("N", "ℕ"),
        MacroTextSpec("lcm", "lcm"),
        MacroTextSpec("lbr", "@@@BRLEFT@@@"),
        MacroTextSpec("bar", "@@@BARSTART@@@%(1)s@@@BAREND@@@"),
        MacroTextSpec("vspace", "@@@VSPACESTART@@@%(1)s@@@VSPACEEND@@@"),
        MacroTextSpec("ord", "ord"),
        MacroTextSpec("gcd", "gcd"),
        MacroTextSpec("mod", "mod"),
    ],
    prepend=True,
)


def preprocess_sub_super_scripts(text):
    """Replaces superscripts/subscripts with safe placeholder tags free of underscores."""
    text = re.sub(r"\^\{([^}]+)\}", r"@@@SUPSTART@@@\1@@@SUPEND@@@", text)
    text = re.sub(
        r"\^([a-zA-Z0-9\+\-]|\\iota)", r"@@@SUPSTART@@@\1@@@SUPEND@@@", text
    )
    text = re.sub(r"_\{([^}]+)\}", r"@@@SUBSTART@@@\1@@@SUBEND@@@", text)
    text = re.sub(r"_([a-zA-Z0-9\+\-])", r"@@@SUBSTART@@@\1@@@SUBEND@@@", text)
    return text


def postprocess_html_tags(text):
    """Converts safe tokens to valid Graphviz HTML labels."""
    # Convert \vspace{N} to a small empty break tag
    text = re.sub(
        r"@@@VSPACESTART@@@(\d+)@@@VSPACEEND@@@",
        r'<BR ALIGN="LEFT"/><FONT POINT-SIZE="\1">&nbsp;</FONT><BR ALIGN="LEFT"/>',
        text
    )
    return (
        text.replace("@@@BOLDSTART@@@", "<B>")
        .replace("@@@BOLDEND@@@", "</B>")
        .replace("@@@SUPSTART@@@", "<SUP>")
        .replace("@@@SUPEND@@@", "</SUP>")
        .replace("@@@SUBSTART@@@", "<SUB>")
        .replace("@@@SUBEND@@@", "</SUB>")
        .replace("@@@BRLEFT@@@", '<BR ALIGN="LEFT"/>')
        .replace("@@@BARSTART@@@", "<O>")
        .replace("@@@BAREND@@@", "</O>")
    )


def find_unknown_macro(node, ctx):
    """ foobar """
    if node is None:
        return None
    if isinstance(node, LatexMacroNode):
        if ctx.get_macro_spec(node.macroname) is None:
            return node
        if hasattr(node, "nodeargd") and node.nodeargd:
            arg_list = getattr(
                node.nodeargd,
                "argnlist",
                getattr(node.nodeargd, "argnodelist", []),
            )
            for child in arg_list:
                err_node = find_unknown_macro(child, ctx)
                if err_node:
                    return err_node
    elif hasattr(node, "nodelist") and node.nodelist:
        for child in node.nodelist:
            err_node = find_unknown_macro(child, ctx)
            if err_node:
                return err_node
    return None

# pylint: disable=too-many-locals
def process_cases_environment(env_node, converter, full_latex_str):
    """ foobar """
    rows = [[]]
    for child in env_node.nodelist:
        if isinstance(child, LatexMacroNode) and child.macroname == "\\":
            rows.append([])
        else:
            rows[-1].append(child)

    table_rows = []
    num_rows = len([r for r in rows if r])

    for row_nodes in rows:
        if not row_nodes:
            continue

        first_pos = row_nodes[0].pos
        last_node = row_nodes[-1]
        last_pos = last_node.pos + last_node.len

        row_str = full_latex_str[first_pos:last_pos]

        if "&" in row_str:
            expr_str, cond_str = row_str.split("&", 1)
        else:
            expr_str, cond_str = row_str, ""

        w_expr = LatexWalker(expr_str, latex_context=walker_ctx)
        n_expr, _, _ = w_expr.get_latex_nodes()
        expr = converter.nodelist_to_text(n_expr).strip()

        w_cond = LatexWalker(cond_str, latex_context=walker_ctx)
        n_cond, _, _ = w_cond.get_latex_nodes()
        cond = converter.nodelist_to_text(n_cond).strip()

        expr = postprocess_html_tags(html.escape(expr))
        cond = postprocess_html_tags(html.escape(cond))

        if len(table_rows) == 0:
            table_rows.append(
                f"<TR>"
                f'<TD ROWSPAN="{num_rows}" VALIGN="MIDDLE" ALIGN="RIGHT" BORDER="0">'
                f'<FONT POINT-SIZE="22">&#123;</FONT></TD>'
                f'<TD ALIGN="LEFT" VALIGN="MIDDLE" BORDER="0">{expr}</TD>'
                f'<TD ALIGN="LEFT" VALIGN="MIDDLE" BORDER="0">&nbsp;&nbsp;&nbsp;&nbsp;{cond}</TD>'
                f"</TR>"
            )
        else:
            table_rows.append(
                f"<TR>"
                f'<TD ALIGN="LEFT" VALIGN="MIDDLE" BORDER="0">{expr}</TD>'
                f'<TD ALIGN="LEFT" VALIGN="MIDDLE" BORDER="0">&nbsp;&nbsp;&nbsp;&nbsp;{cond}</TD>'
                f"</TR>"
            )

    return (
        '<TABLE BORDER="0" CELLBORDER="0" CELLSPACING="0" CELLPADDING="1">'
        + "".join(table_rows)
        + "</TABLE>"
    )


def latex_to_graphviz_html(latex_str):
    """ foobar """
    latex_str = preprocess_sub_super_scripts(latex_str)

    walker = LatexWalker(latex_str, latex_context=walker_ctx)
    nodes, _, _ = walker.get_latex_nodes()

    for node in nodes:
        missing_node = find_unknown_macro(node, l2t_ctx)
        if missing_node:
            raise ValueError(f"Unknown macro \\{missing_node.macroname}")

    converter = LatexNodes2Text(latex_context=l2t_ctx)

    if r"\begin{cases}" in latex_str:
        for node in nodes:
            if (
                isinstance(node, LatexEnvironmentNode)
                and node.environmentname == "cases"
            ):
                cases_table = process_cases_environment(
                    node, converter, latex_str
                )

                prefix_str = latex_str[: node.pos]
                suffix_str = latex_str[node.pos + node.len :]

                if r"\\" in prefix_str:
                    lines = prefix_str.split(r"\\")
                    line1_html = latex_to_graphviz_html(lines[0])[1:-1]
                    line2_html = latex_to_graphviz_html(lines[1])[1:-1]
                    suffix_html = latex_to_graphviz_html(suffix_str)[1:-1]

                    full_html = (
                        '<TABLE BORDER="0" CELLBORDER="0" CELLSPACING="0" CELLPADDING="0">'
                        f'<TR><TD BORDER="0" ALIGN="LEFT" COLSPAN="2">{line1_html}</TD></TR>'
                        f'<TR><TD BORDER="0" VALIGN="MIDDLE" ALIGN="LEFT">{line2_html}</TD>'
                        f'<TD BORDER="0" VALIGN="MIDDLE" ALIGN="LEFT">{cases_table}</TD>'
                        f'<TD BORDER="0" VALIGN="MIDDLE" ALIGN="LEFT">{suffix_html}</TD></TR>'
                        "</TABLE>"
                    )
                    return f"<{full_html}>"

                prefix_html = latex_to_graphviz_html(prefix_str)[1:-1]
                suffix_html = latex_to_graphviz_html(suffix_str)[1:-1]

                full_html = (
                    '<TABLE BORDER="0" CELLBORDER="0" CELLSPACING="0" CELLPADDING="0"><TR>'
                    f'<TD BORDER="0" VALIGN="MIDDLE">{prefix_html}</TD>'
                    f'<TD BORDER="0" VALIGN="MIDDLE">{cases_table}</TD>'
                    f'<TD BORDER="0" VALIGN="MIDDLE">{suffix_html}</TD>'
                    "</TR></TABLE>"
                )
                return f"<{full_html}>"

    plain_text = converter.nodelist_to_text(nodes)
    escaped_text = html.escape(plain_text)

    # Convert placeholders to Graphviz HTML tags for standard nodes
    html_label_body = postprocess_html_tags(escaped_text.replace("\n", "<BR/>"))

    return f"<{html_label_body}>"


def_label = latex_to_graphviz_html(
    r"""\textbf{Def 2.1 }Number-theoretic function:\\"""
    r"""a: \mathbb{N}\to \mathbb{C}"""
)

ex_label = latex_to_graphviz_html(
    r"""\textbf{Ex 2.2a }for s\in\mathbb{C}: \iota^{s}(n) := n^s \forall n \in
        \mathbb{N} is s-th power\\function (s=0 constant one function, identity \iota^1 =: \iota)"""
)

def_3_13_label = latex_to_graphviz_html(
    r"""\textbf{Def 3.13 } Ring R, x\in R: if \exists y\in R\setminus \{0\}: xy=0,
    then x is called zero divisor"""
)

ex_3_14_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.14 } zero divisors in \Z/3\Z: \bar{0}, so has no zero divisors\vspace{3}"""
    r"""zero divisors in \Z/4\Z: \bar{0},\bar{2}, so has zero divisor\\"""
)

def_3_15_label = latex_to_graphviz_html(
    r"""\textbf{Def 3.15 } Ring R, x\in R: if \exists y\in R: xy=1,\\then x is called a unit"""
)

ex_3_16_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.16 } units in \Z/3\Z: \bar{1},\bar{2}\vspace{3}"""
    r"""units in \Z/4\Z: \bar{1},\bar{3}"""
)

prop_3_17_label = latex_to_graphviz_html(
    r"""\textbf{Prop 3.17 } R ring\lbr"""
    r"""(a) R^{\times}:=\{x\in R: x is unit\} with \cdot\ is (abelian) group of units\lbr"""
    r"""(b) x\in R^{\times} \implies\ x no zero divisor\lbr"""
    r"""(c) R finite, then also: x\in R no zero divisor \implies\ x is unit\lbr"""
)

ex_3_18_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.18 } Finite ring R=\Z/n\Z, n\in \N, x\in R:\vspace{5}"""
    r"""\bar{x} unit \iff \bar{x} no zero divisor\lbr """
    r"""Units in R are called coprime residue classes modulo n\lbr """
    r"""(\Z/n\Z)^{\times} is called multiplicative group of integers modulo n"""
)

def_3_19_label = latex_to_graphviz_html(
    r"""\textbf{Def 3.19 } (Commutative) ring R
with R^{\times} = R \setminus \{0\} is called field"""
)

ex_3_20_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.20 } \Z/3\Z\ is field, \Z/4\Z\ and zero ring are no fields."""
)

thm_3_21_label = latex_to_graphviz_html(
    r"""\textbf{Thm 3.21 } n\in \N, these are equivalent\lbr"""
    r"""(i) n is prime\lbr"""
    r"""(ii) \Z/n\Z\ is field\lbr"""
    r"""(iii) \Z/n\Z\ has no zero divisors\lbr"""
)

prop_3_22_label = latex_to_graphviz_html(
    r"""\textbf{Prop 3.22 } a\in \mathbb{N}, \bar{a}\in \Z/n\Z:\vspace{3}"""
    r"""\bar{a}\in (\Z/n\Z)^{\times} \iff \gcd(a,n)=1"""
)

cor_3_23_label = latex_to_graphviz_html(
    r"""\textbf{Cor 3.23 } n\in \mathbb{N}, a\in \Z:\vspace{3}"""
    r"""(\exists x\in \Z: ax\equiv 1 (\mod\ n)) \iff \gcd(a,n)=1"""
)

ex_3_24_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.24 } Solutions for\\"""
    r"""3x\equiv 1 (\mod\ 37): L=25+37\Z"""
)

prop_3_25_label = latex_to_graphviz_html(
    r"""\textbf{Prop 3.25 } a,b\in \Z, n\in\N\\"""
    r"""(\exists x\in\Z: ax\equiv b (\mod\ n)) \iff \gcd(a,n)\vert b"""
)

ex_3_26_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.26 } (a) \nexists x\in \Z: 15x\equiv 7 (\mod\ 21)\lbr"""
    r"""(b) \exists x\in\Z: 15x\equiv 6 (\mod\ 21)\lbr"""
)

def_3_27_label = latex_to_graphviz_html(
    r"""\textbf{Def 3.27 } Order \vert G\vert\ of group\\"""
    r"""is number of its elements"""
)

ex_3_28_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.28 }\vert(\Z/n\Z)^{\times}\vert=\phi(n)"""
)

prop_3_29_label = latex_to_graphviz_html(
    r"""\textbf{Prop 3.29 } G finite abelian group.\lbr
        \forall g\in G: g^{\vert G\vert} =1 """
)

thm_3_30_label = latex_to_graphviz_html(
    r"""\textbf{Thm 3.30 } (Fermat-Euler theorem) \vspace{5}"""
    r"""n\in \mathbb{N}. """
    r"""\forall \bar{a}\in (\Z/n\Z)^{\times}:\ \bar{a}^{\phi(n)} =\bar{1} """
)

ex_3_31_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.31 } 3^{19}\equiv 10 (\mod\ 17)"""
)

cor_3_32_label = latex_to_graphviz_html(
    r"""\textbf{Cor 3.32 } (Fermat's little theorem) p prime:\vspace{3}"""
    r"""(a) \forall \bar{a}\in \mathbb{F}_p^{\times}: \bar{a}^{p-1}=\bar{1}\vspace{5}"""
    r"""(b) \forall \bar{a}\in \mathbb{F}_p: \bar{a}^p=\bar{a}\lbr"""
)

def_3_33_label = latex_to_graphviz_html(
    r"""\textbf{Def 3.33 } Group G is cyclic:\lbr
        \exists g\in G generator with\lbr
        G = \{g^n: n\in \Z\}=:<g>\lbr"""
)

rem_3_34_label = latex_to_graphviz_html(
    r"""\textbf{Rem 3.34 } Every cyclic group is abelian."""
)


ex_3_35_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.35 }(a) group (\Z/5\Z)^{\times} = \{\bar{1},\bar{2},"""
    r"""\bar{3},\bar{4}\} is cyclic\vspace{3}"""
    r"""(b) group (\Z/8\Z)^{\times} = \{\bar{1},\bar{3},\bar{5},\bar{7}\} is not cyclic\lbr"""
    r"""(c) additive group \Z\ is cyclic\vspace{3}"""
    r"""(d) additive group \Z/m\Z =\{\bar{0},\bar{1},\dots,\bar{m-1}\}\ is cyclic\lbr"""
)

def_3_36_label = latex_to_graphviz_html(
    r"""\textbf{Def 3.36 } G finite abelian group.\lbr
        Order \ord(G):=\min\{n\in \mathbb{N}: g^n=1\}\lbr """
)

ex_3_37_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.37 }For G=(\Z/5\Z)^{\times}:\vspace{3}"""
    r"""(a) ord(\bar{2})=4\vspace{3}"""
    r"""(b) ord(\bar{4})=2\lbr"""
)

prop_3_38_label = latex_to_graphviz_html(
    r"""\textbf{Prop 3.38 }G finite abelian group:
        G is cyclic \iff \exists g\in G with ord(g)=\vert G\vert"""
)

prop_3_39_label = latex_to_graphviz_html(
    r"""\textbf{Prop 3.39 }G finite abelian group,\\g\in G, m\in \Z: ord(g)\vert m \iff g^m=1"""
)

cor_3_40_label = latex_to_graphviz_html(
    r"""\textbf{Cor 3.40 } G finite abelian group.\lbr
        \forall g\in G: ord(g) \vert\ \vert G\vert """
)

def_3_41_label = latex_to_graphviz_html(
    r"""\textbf{Def 3.41 } G finite abelian group.\lbr
        Exponent \exp(G):=\min\{n\in \mathbb{N}: g^n=1 \forall g\in G\}\lbr """
)

ex_3_42_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.42 }(a) exp((\Z/5\Z)^{\times})=4\lbr
        (b) exp((\Z/8\Z)^{\times})=2\lbr"""
)

prop_3_43_label = latex_to_graphviz_html(
    r"""\textbf{Prop 3.43 }G finite abelian group G:\lbr """
    r"""(a) \exp(G) \vert\ \vert G\vert\ \lbr """ 
    r"""(b) \exp(G)= \lcm(\{ord(g): g\in G\})\lbr"""
)

def_3_44_label = latex_to_graphviz_html(
    r"""\textbf{Def 3.44 } homomorphism\\ isomorphism, \cong """
)

ex_3_45_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.45 }K field implies\lbr
        det:GL_n(K)\to  K^{\times} homomorphism"""
)

prop_3_46_label = latex_to_graphviz_html(
    r"""\textbf{Prop 3.46 }G, H groups, \psi: G\to\ H homomorphism:\lbr """
    r"""(a) \psi \text{ injective} \iff \text{ker}(\psi):=\{g\in G: \psi(g)=1\}=\{1\}\lbr """ 
    r"""(b) \psi \text{ isomorphism} \text{implies} \psi^{-1}: H\to G isomorphism\lbr"""
)

thm_3_47_label = latex_to_graphviz_html(
    r"""\textbf{Thm 3.47 }For cyclic group G:\\ G \cong \begin{cases}
        \mathbb{Z} & \text{for }G\text{ infinite,}\\
        \Z /|G|\mathbb{Z} & \text{for }G\text{ finite.} \end{cases}"""
)

ex_3_48_label = latex_to_graphviz_html(
    r"""\textbf{Ex 3.48 } (\Z/5\Z)^{\times} \cong \Z/4\Z\\ \psi: \begin{cases}
        \Z/4\Z &\to\ (\Z/5\Z)^{\times}\\
        a &\mapsto\ \bar{2}^a \end{cases}\lbr"""
)

thm_3_49_label = latex_to_graphviz_html(
    r"""\textbf{Thm 3.49 }G finite abelian group:
G is cyclic \iff \exp(G) = \vert G\vert"""
)

dot_content = f"""digraph G {{
    layout=neato;
    overlap="false";
    sep="+15";
    node [shape=box, fontsize=12, margin="0.15,0.1"];

    labelloc=t
    label="3.3 prime residue classes and Fermat-Euler theorem (Def 3.13 — Cor 3.32)\n3.4 cyclic groups (Def 3.33 — Thm 3.49)\n\n "

#    def_2_1 [label={def_label}];
#    ex_2_2a [label={ex_label}];
    def_3_13 [label={def_3_13_label}];
    ex_3_14 [label={ex_3_14_label}];
    def_3_15 [label={def_3_15_label}];
    ex_3_16 [label={ex_3_16_label}];
    prop_3_17 [label={prop_3_17_label}];
    ex_3_18 [label={ex_3_18_label}];
    def_3_19 [label={def_3_19_label}];
    ex_3_20 [label={ex_3_20_label}];
    thm_3_21 [label={thm_3_21_label}];
    prop_3_22 [label={prop_3_22_label}];
    cor_3_23 [label={cor_3_23_label}];
    ex_3_24 [label={ex_3_24_label}];
    prop_3_25 [label={prop_3_25_label}];
    ex_3_26 [label={ex_3_26_label}];
    def_3_27 [label={def_3_27_label}];
    ex_3_28 [label={ex_3_28_label}];
    prop_3_29 [label={prop_3_29_label}];
    thm_3_30 [label={thm_3_30_label}];
    ex_3_31 [label={ex_3_31_label}];
    cor_3_32 [label={cor_3_32_label}];
    def_3_33 [label={def_3_33_label}];
    rem_3_34 [label={rem_3_34_label}];
    ex_3_35 [label={ex_3_35_label}];
    def_3_36 [label={def_3_36_label}];
    ex_3_37 [label={ex_3_37_label}];
    prop_3_38 [label={prop_3_38_label}];
    prop_3_39 [label={prop_3_39_label}];
    cor_3_40 [label={cor_3_40_label}];
    def_3_41 [label={def_3_41_label}];
    ex_3_42 [label={ex_3_42_label}];
    prop_3_43 [label={prop_3_43_label}];
    def_3_44 [label={def_3_44_label}];
    ex_3_45 [label={ex_3_45_label}];
    prop_3_46 [label={prop_3_46_label}];
    thm_3_47 [label={thm_3_47_label}];
    ex_3_48 [label={ex_3_48_label}];
    thm_3_49 [label={thm_3_49_label}];

    def_3_13 -> ex_3_14 [style=dotted];
    def_3_15 -> ex_3_16 [style=dotted];
    {{ def_3_13 def_3_15 }} -> prop_3_17 [style=dotted];
    ex_3_14 -> ex_3_16 [style=invis,arrowhead=none];
    prop_3_17 -> ex_3_18 [style=dotted];
    prop_3_17 -> thm_3_21;
    {{ ex_3_16 def_3_19 }} -> ex_3_20 [style=dotted];
    ex_3_20 -> thm_3_21;
    prop_3_29 -> def_3_36;
    thm_3_21 -> prop_3_22 [style=dotted];
    prop_3_22 -> cor_3_23 [style=dotted];
    def_3_19 -> thm_3_21;
    cor_3_23 -> ex_3_24 [style=dotted];
    cor_3_23 -> prop_3_25 [style=dotted];
    prop_3_25 -> ex_3_26 [style=dotted];
    ex_3_24 -> def_3_27 [style=invis,arrowhead=none];
    prop_3_22 -> ex_3_28;
    def_3_27 -> ex_3_28 [style=dotted];
    def_3_33 -> ex_3_35 [style=dotted];
    def_3_36 -> ex_3_37 [style=dotted];
    thm_3_30 -> {{ ex_3_31 cor_3_32 }};
    {{ ex_3_28 prop_3_29 }} -> thm_3_30;
    ex_3_31 -> cor_3_32 [style=invis,arrowhead=none];
    def_3_33 -> rem_3_34 [style=dotted label="https://gist.github.com/Hermann-SW/12c7644ac0c75b4eb019f76c3f023fe5  "
    URL="https://gist.github.com/Hermann-SW/12c7644ac0c75b4eb019f76c3f023fe5"]
    def_3_41 -> prop_3_43 [style=dotted];
    prop_3_39 -> cor_3_40;
    prop_3_39 -> prop_3_43;
    def_3_44 -> {{ ex_3_45 prop_3_46 }} [style=dotted];
    prop_3_38 -> thm_3_47;
    prop_3_39 -> thm_3_47;
    def_3_36 -> prop_3_38 [style=dotted];
    prop_3_46 -> thm_3_47 [style=dotted];
    prop_3_29 -> cor_3_40;
    def_3_41 -> ex_3_42 [style=dotted];
    {{ ex_3_35 thm_3_47 }} -> ex_3_48;
    {{ prop_3_39 prop_3_43 }} -> thm_3_49;
    prop_3_38 -> thm_3_49;
}}"""

DOTFILENAME = "graph_unicode.dot"
with open(DOTFILENAME, "w", encoding="utf-8") as f:
    f.write(dot_content)

print("Generated .dot file:\n")
print(dot_content)

subprocess.run(
    ["dot", "-Tpdf", DOTFILENAME, "-o", "graph_output.pdf"], check=True
)

https://forum.graphviz.org/t/latex-labels-for-graphviz-work-in-progress/3402
https://forums.raspberrypi.com/viewtopic.php?t=400510
https://www.mersenneforum.org (forum down, no link yet)