How to use the pyquery.pyquery.NoDefault function in pyquery

return [result]
    else:
        return []


def callback(func, *args):
    return func(*args[:func.__code__.co_argcount])


class NoDefault(object):
    def __repr__(self):
        """clean representation in Sphinx"""
        return ''


no_default = NoDefault()
del NoDefault


class FlexibleElement(object):
    """property to allow a flexible api"""
    def __init__(self, pget, pset=no_default, pdel=no_default):
        self.pget = pget
        self.pset = pset
        self.pdel = pdel

    def __get__(self, instance, klass):
        class _element(object):
            """real element to support set/get/del attr and item and js call
            style"""
            def __call__(prop, *args, **kwargs):
                return self.pget(instance, *args, **kwargs)

if type(result) is list:
        return result
    elif isinstance(result, etree._ElementTree):
        return [result.getroot()]
    else:
        return [result]

def callback(func, *args):
    return func(*args[:func_code(func).co_argcount])

class NoDefault(object):
    def __repr__(self):
        """clean representation in Sphinx"""
        return ''

no_default = NoDefault()
del NoDefault

class FlexibleElement(object):
    """property to allow a flexible api"""
    def __init__(self, pget, pset=no_default, pdel=no_default):
        self.pget = pget
        self.pset = pset
        self.pdel = pdel
    def __get__(self, instance, klass):
        class _element(object):
            """real element to support set/get/del attr and item and js call
            style"""
            def __call__(prop, *args, **kwargs):
                return self.pget(instance, *args, **kwargs)
            __getattr__ = __getitem__ = __setattr__ = __setitem__ = __call__
            def __delitem__(prop, name):