@abc.abstractmethod<EOL><INDENT>def has_end_reason(self):<DEDENT>
return<EOL>
Tests if a reason this relationship came to an end is known.

        :return: ``true`` if an end reason is available, ``false`` otherwise
        :rtype: ``boolean``
        :raise: ``IllegalState`` -- ``is_effective()`` is ``true``

        *compliance: mandatory -- This method must be implemented.*