def _pickleFunction(f):
    """
    Reduce, in the sense of L{pickle}'s C{object.__reduce__} special method, a
    function object into its constituent parts.

    @param f: The function to reduce.
    @type f: L{types.FunctionType}

    @return: a 2-tuple of a reference to L{_unpickleFunction} and a tuple of
        its arguments, a 1-tuple of the function's fully qualified name.
    @rtype: 2-tuple of C{callable, native string}
    """
    if f.__name__ == '<lambda>':
        raise _UniversalPicklingError(
            "Cannot pickle lambda function: {}".format(f))
    return (_unpickleFunction,
            tuple([".".join([f.__module__, f.__qualname__])]))

    Reduce, in the sense of L{pickle}'s C{object.__reduce__} special method, a
    function object into its constituent parts.

    @param f: The function to reduce.
    @type f: L{types.FunctionType}

    @return: a 2-tuple of a reference to L{_unpickleFunction} and a tuple of
        its arguments, a 1-tuple of the function's fully qualified name.
    @rtype: 2-tuple of C{callable, native string}
    
stackoverflow/venv/lib/python3.6/site-packages/twisted/persisted/styles.py