returns list of items marked as `next up`

    |coro|

    Parameters
    ----------
    userId : str
      if provided, then the list returned is
      the one that that use will see.

    Returns
    -------
    list
      the itmes that will appear as next up
      (for user if id was given)

async def nextUp(self, userId=None):
    '''returns list of items marked as `next up`

    |coro|

    Parameters
    ----------
    userId : str
      if provided, then the list returned is
      the one that that use will see.

    Returns
    -------
    list
      the itmes that will appear as next up
      (for user if id was given)
    '''
    json = await self.connector.getJson('/Shows/NextUp',
                                        pass_uid=True,
                                        remote=False,
                                        userId=userId
    )
    return await self.process(json)