How to use the awe.view.CustomElement._is_custom function in awe

def register(self, custom_element_cls):
        """
        Register a new custom element.

        Not that there is not need to explicitly call this method. When creating a new custom element,
        the element will be registered for you if it isn't already registered.

        :param custom_element_cls: A subclass of ``CustomElement``.
        """
        assert CustomElement._is_custom(custom_element_cls)
        if custom_element_cls._registered:
            return
        self._register(custom_element_cls, obj_id=custom_element_cls.__name__)
        custom_element_cls._registered = True
        self._dispatch({'type': 'refresh'})

This method can return different results depending on ``obj`` type.

        If ``obj`` is a class that inherits from Element, a new element of that type will be created.
        If ``obj`` is a dict or list, it will be parsed and the parser result will be created.
        If ``obj`` is a string, it will be yaml loaded and that result will be passed to the parser.

        When result is passed to the parser, an additional ``inputs`` argument can be supplied as a dict from keys
        to values that are referenced in the DSL using the ``$`` intrinsic function.

        :param obj: The ``Element`` subclass, a dict/list or a string to be passed to the parser.
        :param kwargs: Arguments that should be passed to the ``_init`` method of the created element or one of
                       ``props``, ``style``, ``id``, ``inputs`` if valid.
        :return: The created element.
        """
        from . import parser
        if CustomElement._is_custom(obj) and not obj._registered:
            self.register(obj)
        if parser.is_parsable(obj):
            context = parser.ParserContext(inputs=kwargs.pop('inputs', None))
            element_configuration = self._parse(obj, context)
            return self._new_children(element_configuration, **kwargs)
        else:
            return self._new_child(obj, **kwargs)