code: def _valid_choices(cla55: type) -> Dict[str, str]:
      
      valid_choices: Dict[str, str] = {}
  
      if cla55 not in Registrable._registry:
          raise ValueError(f"{cla55} is not a known Registrable class")
  
      for name, subclass in Registrable._registry[cla55].items():
          # These wrapper classes need special treatment
          if isinstance(subclass, (_Seq2SeqWrapper, _Seq2VecWrapper)):
              subclass = subclass._module_class
  
          valid_choices[name] = full_name(subclass)
  
      return valid_choices
docs: Return a mapping {registered_name -> subclass_name}
      for the registered subclasses of `cla55`.