def _getDeprecationWarningString(fqpn, version, format=None, replacement=None):
    """
    Return a string indicating that the Python name was deprecated in the given
    version.

    @param fqpn: Fully qualified Python name of the thing being deprecated
    @type fqpn: C{str}

    @param version: Version that C{fqpn} was deprecated in.
    @type version: L{incremental.Version}

    @param format: A user-provided format to interpolate warning values into, or
        L{DEPRECATION_WARNING_FORMAT
        <twisted.python.deprecate.DEPRECATION_WARNING_FORMAT>} if L{None} is
        given.
    @type format: C{str}

    @param replacement: what should be used in place of C{fqpn}. Either pass in
        a string, which will be inserted into the warning message, or a
        callable, which will be expanded to its full import path.
    @type replacement: C{str} or callable

    @return: A textual description of the deprecation
    @rtype: C{str}
    """
    if format is None:
        format = DEPRECATION_WARNING_FORMAT
    warningString = format % {
        'fqpn': fqpn,
        'version': getVersionString(version)}
    if replacement:
        warningString = "%s; %s" % (
            warningString, _getReplacementString(replacement))
    return warningString

    Return a string indicating that the Python name was deprecated in the given
    version.

    @param fqpn: Fully qualified Python name of the thing being deprecated
    @type fqpn: C{str}

    @param version: Version that C{fqpn} was deprecated in.
    @type version: L{incremental.Version}

    @param format: A user-provided format to interpolate warning values into, or
        L{DEPRECATION_WARNING_FORMAT
        <twisted.python.deprecate.DEPRECATION_WARNING_FORMAT>} if L{None} is
        given.
    @type format: C{str}

    @param replacement: what should be used in place of C{fqpn}. Either pass in
        a string, which will be inserted into the warning message, or a
        callable, which will be expanded to its full import path.
    @type replacement: C{str} or callable

    @return: A textual description of the deprecation
    @rtype: C{str}
    
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/deprecate.py