code: def get_action(self, key):
          
          index_local_timestamp = self.get_index_local_timestamp(key)
          real_local_timestamp = self.get_real_local_timestamp(key)
          remote_timestamp = self.get_remote_timestamp(key)
          return get_sync_state(
              index_local_timestamp, real_local_timestamp, remote_timestamp
          )
docs: returns the action to perform on this key based on its
          state before the last sync.