Creates a tag using the decorated func as the render function
        for the template tag node. The render function takes two
        arguments - the template context and the tag token.

def render_tag(self, tag_func):
        """
        Creates a tag using the decorated func as the render function
        for the template tag node. The render function takes two
        arguments - the template context and the tag token.
        """
        @wraps(tag_func)
        def tag_wrapper(parser, token):
            class RenderTagNode(template.Node):
                def render(self, context):
                    return tag_func(context, token)
            return RenderTagNode()
        return self.tag(tag_wrapper)