def __get__(self, model_instance, model_class):
    if model_instance is None:
      return self
    if hasattr(model_instance, self.__id_attr_name()):
      reference_id = getattr(model_instance, self.__id_attr_name())
    else:
      reference_id = None
    if reference_id is not None:
      resolved = getattr(model_instance, self.__resolved_attr_name())
      if resolved is not None:
        return resolved
      else:
        instance = get(reference_id)
        if instance is None:
          raise Error('ReferenceProperty failed to be resolved')
        setattr(model_instance, self.__resolved_attr_name(), instance)
        return instance
    else:
      return None
Checks whether a value is:
dataset/ETHPy150Open CollabQ/CollabQ/.google_appengine/google/appengine/ext/db/__init__.py/ReferenceProperty.__get__--crossover with--dataset/ETHPy150Open manjitkumar/drf-url-filters/filters/validations.py/Alphanumeric