code: def failback(self, force_full_copy=None):
          
          req_body = self._cli.make_body(forceFullCopy=force_full_copy)
          resp = self.action('failback', **req_body)
          resp.raise_if_err()
          return resp
docs: Fails back a replication session.
  
          This can be applied on a replication session that is failed over. Fail
          back will synchronize the changes done to original destination back to
          original source site and will restore the original direction of
          session.
  
          :param force_full_copy: indicates whether to sync back all data from
              the destination SP to the source SP during the failback session.
              True - Sync back all data.
              False - Sync back changed data only.