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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 _combine_indexers(old_key, shape, new_key):
 """ Combine two indexers. Parameters old_key: ExplicitIndexer The first indexer for the original array shape: tuple of ints Shape of the original array to be indexed by old_key new_key: The second indexer for indexing original[old_key] """

    if not isinstance(old_key, VectorizedIndexer):
        old_key = _outer_to_vectorized_indexer(old_key, shape)
    if len(old_key.tuple) == 0:
        return new_key

    new_shape = np.broadcast(*old_key.tuple).shape
    if isinstance(new_key, VectorizedIndexer):
        new_key = _arrayize_vectorized_indexer(new_key, new_shape)
    else:
        new_key = _outer_to_vectorized_indexer(new_key, new_shape)

    return VectorizedIndexer(tuple(o[new_key.tuple] for o in
                                   np.broadcast_arrays(*old_key.tuple)))