docs: def register_output_name(self, input_folder, rel_name, rel_output_name):
          """Register proper and improper file mappings."""
          self.improper_input_file_mapping[rel_name].add(rel_output_name)
          self.proper_input_file_mapping[os.path.join(input_folder, rel_name)] = rel_output_name
          self.proper_input_file_mapping[rel_output_name] = rel_output_name