docs: def search(self, line):
          """CN search."""
          if self._session.get(d1_cli.impl.session.QUERY_ENGINE_NAME) == "solr":
              return self._search_solr(line)
          raise d1_cli.impl.exceptions.InvalidArguments(
              "Unsupported query engine: {}".format(
                  self._session.get(d1_cli.impl.session.QUERY_ENGINE_NAME)
              )
          )