Gets the session for assigning temporal coverage of an asset for
        the given repository.

        arg:    repository_id (osid.id.Id): the Id of the repository
        arg     proxy (osid.proxy.Proxy): a proxy
        return: (osid.repository.AssetTemporalAssignmentSession) - an
                AssetTemporalAssignmentSession
        raise:  NotFound - repository_id not found
        raise:  NullArgument - repository_id is null
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - supports_asset_temporal_assignment() or
                supports_visible_federation() is false
        compliance: optional - This method must be implemented if
                    supports_asset_temporal_assignment() and
                    supports_visible_federation() are true.

def get_asset_temporal_assignment_session_for_repository(self, repository_id, proxy):
        """Gets the session for assigning temporal coverage of an asset for
        the given repository.

        arg:    repository_id (osid.id.Id): the Id of the repository
        arg     proxy (osid.proxy.Proxy): a proxy
        return: (osid.repository.AssetTemporalAssignmentSession) - an
                AssetTemporalAssignmentSession
        raise:  NotFound - repository_id not found
        raise:  NullArgument - repository_id is null
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - supports_asset_temporal_assignment() or
                supports_visible_federation() is false
        compliance: optional - This method must be implemented if
                    supports_asset_temporal_assignment() and
                    supports_visible_federation() are true.

        """
        if not repository_id:
            raise NullArgument()
        if not self.supports_asset_temporal_assignment():
            raise Unimplemented()
        try:
            from . import sessions
        except ImportError:
            raise OperationFailed('import error')
        proxy = self._convert_proxy(proxy)
        try:
            session = sessions.AssetTemporalAssignmentSession(repository_id, proxy, runtime=self._runtime)
        except AttributeError:
            raise OperationFailed('attribute error')
        return session