code: def _validate_page(self):
          
          for ocrd_file in self.mets.find_files(mimetype=MIMETYPE_PAGE, local_only=True):
              self.workspace.download_file(ocrd_file)
              page_report = PageValidator.validate(ocrd_file=ocrd_file, strictness=self.page_strictness)
              self.report.merge_report(page_report)
docs: Run PageValidator on the PAGE-XML documents referenced in the METS.