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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 _ranges_key(r, delta_indices):
 """Sorting key for ranges. When used with ``reverse=True``, this can be used to sort index ranges into the order we would prefer to eliminate them by evaluating KroneckerDeltas: First, eliminate primed indices, then indices names higher in the alphabet. """

    idx = r.index_symbol
    if idx in delta_indices:
        return (r.index_symbol.primed, r.index_symbol.name)
    else:
        # ranges that are not in delta_indices should remain in the original
        # order
        return (0, ' ')