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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 _get_index(n_items, item_size, n):
 """Prepare an index attribute for GPU uploading."""

    index = np.arange(n_items)
    index = np.repeat(index, item_size)
    index = index.astype(np.float64)
    assert index.shape == (n,)
    return index