code: def _make_class(cls, **kwargs):
      
      kwargs = {k: (v if v is not None else getattr(cls, k, None))
                for k, v in kwargs.items()}
      # The class name contains a hash of the custom parameters.
      name = cls.__name__ + '_' + _hash(kwargs)
      if name not in _CLASSES:
          logger.log(5, "Create class %s %s.", name, kwargs)
          cls = type(name, (cls,), kwargs)
          _CLASSES[name] = cls
      return _CLASSES[name]
docs: Return a custom Visual class with given parameters.