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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def MultiNotifyQueue(self, notifications, mutation_pool=None):
 """This is the same as NotifyQueue but for several session_ids at once. Args: notifications: A list of notifications. mutation_pool: A MutationPool object to schedule Notifications on. Raises: RuntimeError: An invalid session_id was passed. """

    extract_queue = lambda notification: notification.session_id.Queue()
    for queue, notifications in iteritems(
        collection.Group(notifications, extract_queue)):
      self._MultiNotifyQueue(queue, notifications, mutation_pool=mutation_pool)