@abc.abstractmethod<EOL><INDENT>def alias_item(self, item_id, alias_id):<DEDENT>
pass<EOL>
Adds an ``Id`` to an ``Item`` for the purpose of creating compatibility.

        The primary ``Id`` of the ``Item`` is determined by the
        provider. The new ``Id`` is an alias to the primary ``Id``. If
        the alias is a pointer to another item, it is reassigned to the
        given item ``Id``.

        :param item_id: the ``Id`` of an ``Item``
        :type item_id: ``osid.id.Id``
        :param alias_id: the alias ``Id``
        :type alias_id: ``osid.id.Id``
        :raise: ``AlreadyExists`` -- ``alias_id`` is in use as a primary ``Id``
        :raise: ``NotFound`` -- ``item_id`` not found
        :raise: ``NullArgument`` -- ``item_id`` or ``alias_id`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure occurred

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