'Get the items in a playlist specified by ``uri``.
Returns a list of :class:`~mopidy.models.Ref` objects referring to the
playlist\'s items.
If a playlist with the given ``uri`` doesn\'t exist, it returns
:class:`None`.
:rtype: list of :class:`mopidy.models.Ref`, or :class:`None`
.. versionadded:: 1.0'

def get_items(self, uri):

    raise NotImplementedError
