def leave(list_id, email):
    """Unsubscribe from a mailing list.

        :param list_id: The list id of the mailing list the user is
            unsubscribing from.
        :type list_id: string
        :param email: The email address of the user getting unsubscribed.
        :type email: string
        :raises InvalidEmailAddressError: if the email address is not valid.
        :raises NoSuchListError: if the named mailing list does not exist.
        :raises NotAMemberError: if the given address is not a member of the
            mailing list.
        """
