Demo of overriding the function definition check in PyFlakes via subclass method, adapted from https://github.com/PyCQA/pyflakes/blob/master/pyflakes/api.py

check.py

    import ast

from pyflakes import checker, reporter


class CheckerSnooper(checker.Checker):
    verbose: bool

    def __init__(self, *args, **kwargs):
        self.verbose = kwargs.pop("verbose", False)
        super().__init__(*args, **kwargs)

    def FUNCTIONDEF(self, node):
        super().FUNCTIONDEF(node)
        line_range = f"{node.lineno}-{node.end_lineno}"
        info = f"{type(node).__name__} {node.name!r} ({line_range=})"
        setattr(node, "depth", self.get_ancestors(node, count=True))
        if self.verbose:
            print(f"{info} depth={node.depth} -> {node.returns.id}")

    def get_ancestors(self, node, count=False) -> int:
        ancestors = []
        while parent := self.getParent(node):
            if count and hasattr(node, "depth"):
                return node.depth + len(ancestors)
            ancestors.append(parent)
            if parent is self.root:
                return len(ancestors) if count else ancestors
            node = parent


def parse(codestring, filename="", verbose=False) -> CheckerSnooper | None:
    report = reporter._makeDefaultReporter()
    try:
        tree = ast.parse(codestring, filename=filename)
    except SyntaxError as e:
        report.syntaxError(filename, e.args[0], e.lineno, e.offset, e.text)
    except Exception:
        report.unexpectedError(filename, "problem decoding source")
    else:
        w = CheckerSnooper(tree, filename=filename, verbose=verbose)
        w.messages.sort(key=lambda m: m.lineno)
        if verbose:
            for m in w.messages:
                print(
                    f"• {type(m).__name__} {list(m.message_args)}",
                    f"L{m.lineno} col {m.col} in {filename or 'STDIN'}",
                )
        return w
    return None


codestring = """
def DummyFunction(a: int) -> int:
    class InnerClass():
        def dummy_inner_class_method() -> int:
            x = 2
            return 1
    return a + InnerClass().dummy_inner_class_method()
"""