def usedby_packages(self, deps_file_path=None, depslock_file_path=None, packages=None):
        """
        Lock packages. Downloader search packages
        """
        if deps_file_path is None:
            deps_file_path = self._deps_path
        if depslock_file_path is None:
            depslock_file_path = self._depslock_path
        if deps_file_path == depslock_file_path:
            depslock_file_path += '.lock'

        if packages is None:
            self.search_dependencies(deps_file_path)
        else:
            self._root_package.packages = packages
        self._log.info('Done!')