No, by default check_schema is False because the check is expensive: one has to parse all the generated XML and compare it with the schema. What I did is to perform the check in the tests (see the function check_export in export/hazard_test.py) so that we may be sure that at least for the test data we are always generating valid files. This approach works and actually I have discovered another case where we were generating invalid files (the UHS files).