class root_topic_1:
    """root topic 1"""

    class subtopic_2:
        "subtopic 2"

        class subsubtopic_21:
            """Sub sub topic 1 of subtopic 2."""
            def msgDataSpec(arg1, arg2=None, arg4=None):
                """
                - arg4: doc for arg4
                """
                pass


class root_topic_2:
    'docs for root_topic_2'

    class subtopic_21:
        'docs for subtopic_21'