Extract subelement from obj, according to pointer.
        It assums that document is the object.

        :param obj: the object source
        :param bypass_ref: disable JSON Reference errors

def extract(self, obj, bypass_ref=False):
        """
        Extract subelement from obj, according to pointer.
        It assums that document is the object.

        :param obj: the object source
        :param bypass_ref: disable JSON Reference errors
        """
        return self.pointer.extract(obj, bypass_ref)