Will return True if hunt's task was assigned to this client before.

def _CheckIfHuntTaskWasAssigned(self, client_id, hunt_id):
    """Will return True if hunt's task was assigned to this client before."""
    if data_store.RelationalDBEnabled():
      flow_id = hunt_id
      if hunt.IsLegacyHunt(hunt_id):
        # Strip "H:" prefix.
        flow_id = flow_id[2:]

      try:
        data_store.REL_DB.ReadFlowObject(client_id, flow_id)
        return True
      except db.UnknownFlowError:
        pass
    else:
      client_urn = rdfvalue.RDFURN(client_id)
      for _ in aff4.FACTORY.Stat([
          client_urn.Add("flows/%s:hunt" % rdfvalue.RDFURN(hunt_id).Basename())
      ]):
        return True

    return False