code: def gen_typedefs(self) -> str:
          
          rval = []
          for typ in self.schema.types.values():
              typname = self.python_name_for(typ.name)
              parent = self.python_name_for(typ.typeof)
              rval.append(f'class {typname}({parent}):\n\tpass')
          return '\n\n\n'.join(rval) + ('\n' if rval else '')
docs: Generate python type declarations for all defined types