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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 dequeue(self) -> Tuple[int, TItem]: """Removes and returns an item from the priority queue. Returns: A tuple whose first element is the priority of the dequeued item and whose second element is the dequeued item. Raises: ValueError: The queue is empty. """

        if self._len == 0:
            raise ValueError('BucketPriorityQueue is empty.')

        # Drop empty buckets at the front of the queue.
        while self._buckets and not self._buckets[0]:
            self._buckets.pop(0)
            self._offset += 1

        # Pull item out of the front bucket.
        item = self._buckets[0].pop(0)
        priority = self._offset
        self._len -= 1
        if self._drop_set is not None:
            self._drop_set.remove((priority, item))

        # Note: do not eagerly clear out empty buckets after pulling the item!
        # Doing so increases the worst case complexity of "monotonic" use from
        # O(N+P) to O(N*P).

        return priority, item