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."""
    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