docs: def _set_op(self, node):
          """
          Translate a set operator node into SQLQuery.
          :param node: a treebrd node
          :return: a SQLQuery object for the tree rooted at node
          """
          select_block = str(node.attributes)
          from_block = '({left} {operator} ALL {right}) AS {name}'.format(
              left=self.translate(node.left).to_sql(),
              right=self.translate(node.right).to_sql(),
              operator=self._get_sql_operator(node), name=self._get_temp_name(node))
          return self.query(select_block=select_block, from_block=from_block)