@abc.abstractmethod<EOL><INDENT>def remove_alias(self, primary_id, equivalent_id):<DEDENT>
pass<EOL>
Removes equivalence from two ``Ids``.

        :param primary_id: the primary ``Id``
        :type primary_id: ``osid.id.Id``
        :param equivalent_id: the equivalent ``Id``
        :type equivalent_id: ``osid.id.Id``
        :raise: ``NotFound`` -- ``primary_id`` or ``equivalent_id`` is not found or ``equivalent_id`` not mapped to ``primary_id``
        :raise: ``NullArgument`` -- ``primary_id`` or ``equivalent_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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