Removes all labels for a given client.

    Args:
      client_id: The client_id.
      labels: A list of labels to remove.

def RemoveClientLabels(self, client_id, labels):
    """Removes all labels for a given client.

    Args:
      client_id: The client_id.
      labels: A list of labels to remove.
    """
    for label in labels:
      keyword = self._NormalizeKeyword(label)
      # This might actually delete a keyword with the same name as the label (if
      # there is one).
      data_store.REL_DB.RemoveClientKeyword(client_id, keyword)
      data_store.REL_DB.RemoveClientKeyword(client_id, "label:%s" % keyword)