def test_multiPart(self):
        """
        For a I{multipart/*} message, L{imap4.getBodyStructure} returns a list
        containing the body structure information for each part of the message
        followed by an element giving the MIME subtype of the message.
        """
        oneSubPart = FakeyMessage({
                'content-type': 'image/jpeg; x=y',
                'content-id': 'some kind of id',
                'content-description': 'great justice',
                'content-transfer-encoding': 'maximum',
                }, (), b'', b'hello world', 123, None)

        anotherSubPart = FakeyMessage({
                'content-type': 'text/plain; charset=us-ascii',
                }, (), b'', b'some stuff', 321, None)

        container = FakeyMessage({
                'content-type': 'multipart/related',
                }, (), b'', b'', 555, [oneSubPart, anotherSubPart])

        self.assertEqual(
            [imap4.getBodyStructure(oneSubPart),
             imap4.getBodyStructure(anotherSubPart),
             'related'],
            imap4.getBodyStructure(container))

        For a I{multipart/*} message, L{imap4.getBodyStructure} returns a list
        containing the body structure information for each part of the message
        followed by an element giving the MIME subtype of the message.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_imap.py