Django code to make a multi-checkbox widget that works with Django's Postgres-based ArrayField

forms.py

from django import forms
from django.forms import widgets


DELIMITER = ','


class MultiCheckboxChoiceInput(widgets.CheckboxChoiceInput):

    def __init__(self, *args, **kwargs):
        # yes, we *do* want the super class's super class --
        # widgets.CheckboxChoiceInput's __init__ would take our comma-delimited
        # string and turn it into a set of individual characters.
        super(widgets.CheckboxChoiceInput, self).__init__(*args, **kwargs)

    def is_checked(self):
        # We're counting on alignment btw this class's delimiter and
        # ArrayFieldCheckboxSelectMultiple's -- not ideal
        values = set(self.value.split(DELIMITER))
        return self.choice_value in values


class CheckboxFieldRenderer(widgets.ChoiceFieldRenderer):
    choice_input_class = MultiCheckboxChoiceInput


class ArrayFieldCheckboxSelectMultiple(forms.CheckboxSelectMultiple):
    """This is a Form Widget for use with a Postgres ArrayField. It implements
    a multi-select interface that can be given a set of `choices`.

    Derived from https://bradmontgomery.net/blog/nice-arrayfield-widgets-choices-and-chosenjs/
    """
    renderer = CheckboxFieldRenderer

    def render_options(self, choices, value):
        # value *should* be a list, but it might be a delimited string.
        if isinstance(value, str):
            value = value.split(DELIMITER)
        return super(ArrayFieldCheckboxSelectMultiple, self).render_options(
            choices, value)

    def value_from_datadict(self, data, files, name):
        # Normally, we'd want a list here, which is what we get from the
        # CheckboxSelectMultiple superclass, but the SimpleArrayField expects
        # to get a delimited string, so we're doing a little extra work.
        return DELIMITER.join(data.getlist(name))