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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 zscore(arr):
 """Return arr normalized with mean 0 and unit variance. If the input has 0 variance, the result will also have 0 variance. Parameters arr : array-like Returns ------- zscore : array-like Examples -------- Compute the z score for a small array: array([ 1., -1.]) 0.0 1.0 Does not re-scale in case the input is constant (has 0 variance):
 array([ 0., 0.]) """

    arr = arr - np.mean(arr)
    std = np.std(arr)
    if std != 0:
        arr /= std
    return arr