ndb.py 文件源码

def convert_KeyProperty(self, model, prop, kwargs):
        """Returns a form field for a ``ndb.KeyProperty``."""
        if 'reference_class' not in kwargs:
            try:
                reference_class = prop._kind
            except AttributeError:
                reference_class = prop._reference_class

            if isinstance(reference_class, string_types):
                # reference class is a string, try to retrieve the model object.
                mod = __import__(model.__module__, None, None, [reference_class], 0)
                reference_class = getattr(mod, reference_class)
            kwargs['reference_class'] = reference_class
        kwargs.setdefault('allow_blank', not prop._required)
        return KeyPropertyField(**kwargs)