def time_str_from_datetime_str(date_string: str) -> str:
    """
    Extracts the time parts of a datetime.

    Example:
        2019-12-03T09:00:00.12345 will be converted to:
        09:00:00.12345

    :param date_string:
    :return:
    """
    return date_string.split('T')[1]