docs: private void validateModality(SqlNode query) {
  		final SqlModality modality = deduceModality(query);
  		if (query instanceof SqlSelect) {
  			final SqlSelect select = (SqlSelect) query;
  			validateModality(select, modality, true);
  		} else if (query.getKind() == SqlKind.VALUES) {
  			switch (modality) {
  				case STREAM:
  					throw newValidationError(query, Static.RESOURCE.cannotStreamValues());
  			}
  		} else {
  			assert query.isA(SqlKind.SET_QUERY);
  			final SqlCall call = (SqlCall) query;
  			for (SqlNode operand : call.getOperandList()) {
  				if (deduceModality(operand) != modality) {
  					throw newValidationError(operand,
  						Static.RESOURCE.streamSetOpInconsistentInputs());
  				}
  				validateModality(operand);
  			}
  		}
  	}