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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 classify_coupling(coupling):
 """Return a constant indicating the type of coupling. Depending on the type of coupling, one of the constants from :class:`.CouplingClass` is returned. Args: coupling: Tuple of minimum and maximum flux ratio """

    lower, upper = coupling

    if lower is None and upper is None:
        return CouplingClass.Uncoupled
    elif lower is None or upper is None:
        return CouplingClass.DirectionalReverse
    elif lower == 0.0 and upper == 0.0:
        return CouplingClass.Inconsistent
    elif lower <= 0.0 and upper >= 0.0:
        return CouplingClass.DirectionalForward
    elif abs(lower - upper) < 1e-6:
        return CouplingClass.Full
    else:
        return CouplingClass.Partial