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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 interval_overlap(a, b, x, y):
 """Returns by how much two intervals overlap assumed that a <= b and x <= y"""

    if b <= x or a >= y:
        return 0
    elif x <= a <= y:
        return min(b, y) - a
    elif x <= b <= y:
        return b - max(a, x)
    elif a >= x and b <= y:
        return b - a
    else:
        assert False