def get_composition_lookup_session_for_repository(self, repository_id, proxy):
        """Gets the OsidSession associated with the composition lookup
        service 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.CompositionLookupSession) - the new
                CompositionLookupSession
        raise:  NotFound - repository_id not found
        raise:  NullArgument - repository_id is null
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - supports_composition_lookup() or
                supports_visible_federation() is false
        compliance: optional - This method must be implemented if
                    supports_composition_lookup() and
                    supports_visible_federation() are true.

        """
        if repository_id is None:
            raise NullArgument()
        if not self.supports_composition_lookup():
            raise Unimplemented()
        try:
            from . import sessions
        except ImportError:
            raise  # OperationFailed()
        proxy = self._convert_proxy(proxy)
        try:
            session = sessions.CompositionLookupSession(repository_id, proxy, runtime=self._runtime)
        except AttributeError:
            raise  # OperationFailed()
        return session