>>> t.add_member('AC', 'A', 'C')
        >>> t.add_member('BC', 'B', 'C')
        >>> t.members
        {'AB': ['A', 'B'], 'AC': ['A', 'C'], 'BC': ['B', 'C']}
        >>> t.remove_member('AC')
        >>> t.members
        {'AB': ['A', 'B'], 'BC': ['B', 'C']}
        z"No such member exists in the Trussr