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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 normalize_bound(bound):
 """ Replace ``None`` with + or - inf in bound tuples. Examples -------- (2.6, 7.2) (-inf, 7.2) (2.6, inf) (-inf, inf) This operation is idempotent: (-inf, inf) """

    min_, max_ = bound

    if min_ is None:
        min_ = -float('inf')

    if max_ is None:
        max_ = float('inf')

    return min_, max_