Return a list of (TypedField attribute name, TypedField object)
        tuples for this Entity.

def typed_fields_with_attrnames(cls):
        """Return a list of (TypedField attribute name, TypedField object)
        tuples for this Entity.
        """
        # Checking cls._typed_fields could return a superclass _typed_fields
        # value. So we check our class __dict__ which does not include
        # inherited attributes.
        klassdict = cls.__dict__

        try:
            return klassdict["_typed_fields_with_attrnames"]
        except KeyError:
            # No typed_fields set on this Entity yet. Find them and store
            # them in the _typed_fields class attribute.
            from . import fields
            typed_fields = tuple(fields.iterfields(cls))
            cls._typed_fields_with_attrnames = typed_fields
        return typed_fields