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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 scatter(slope, zero, x1, x2, x1err=[], x2err=[]):
 """ Used mainly to measure scatter for the BCES best-fit """

    n = len(x1)
    x2pred = zero + slope * x1
    s = sum((x2 - x2pred) ** 2) / (n - 1)
    if len(x2err) == n:
        s_obs = sum((x2err / x2) ** 2) / n
        s0 = s - s_obs
    print numpy.sqrt(s), numpy.sqrt(s_obs), numpy.sqrt(s0)
    return numpy.sqrt(s0)