docs: def use(self, client_key):
          """
          :param client_key: The client key.
          :type client_key: str
          :return: The Orchestrator instance (method chaining)
          :rtype: :class:`revision.orchestrator.Orchestrator`
          """
          if not self.clients.has_client(client_key):
              raise ClientNotExist()
  
          self.current_client = self.clients.get_client(client_key)
  
          return self