code: def client(self):
          
          if eventlet:
              with self.client_lock:
                  self._set_client()
          else:
              self._set_client()
          return self._client
docs: Return a lazy-instantiated pymongo client.
  
          When running with eventlet, connection causes IO and can result in more
          than one MongoDB client getting instantiatied, so we wrap the code in
          a semaphore to make sure only one mongodb client is instantiated per
          SimplDB class.