warn when entering extra-install-requiring-section in a lib

my_package.ext.__init__.py

import warnings
from importlib import import_module
from importlib.metadata import requires

from packaging.requirements import Requirement

MY_LIB = "my_lib"
CURRENT_EXTRA = "my_extra"


for req in map(Requirement, requires(MY_LIB)):
    if req.marker is None:
        continue
    if CURRENT_EXTRA in {e[2].value for e in req.marker._markers if e[0].value == "extra"}:
        try:
            import_module(dep)
        except ImportError:
            warnings.warn(
                f"The feature you're trying to use requires the extra '{CURRENT_EXTRA}', install it by running 'pip install "
                f"{MY_LIB}[{CURRENT_EXTRA}]' or 'poetry add {MY_LIB}[{CURRENT_EXTRA}]'."
            )