docs: private SqlModality deduceModality(SqlNode query) {
  		if (query instanceof SqlSelect) {
  			SqlSelect select = (SqlSelect) query;
  			return select.getModifierNode(SqlSelectKeyword.STREAM) != null
  				? SqlModality.STREAM
  				: SqlModality.RELATION;
  		} else if (query.getKind() == SqlKind.VALUES) {
  			return SqlModality.RELATION;
  		} else {
  			assert query.isA(SqlKind.SET_QUERY);
  			final SqlCall call = (SqlCall) query;
  			return deduceModality(call.getOperandList().get(0));
  		}
  	}