code: public List<Field> editorFields() {
          List<Field> editorFields = new ArrayList<>();
          for (Field f : fields) if (f.requirement == REQUIRED || f.requirement == OPTIONAL || f.requirement == EDITOR) {
              editorFields.add(f);
          }
          return editorFields;
      }
docs: Get only those fields included in the official GTFS specification for this table or used by the editor.