docs: 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)))