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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 rnegative_binomial(mu, alpha, size=None):
 """ Random negative binomial variates. """

    # Using gamma-poisson mixture rather than numpy directly
    # because numpy apparently rounds
    mu = np.asarray(mu, dtype=float)
    pois_mu = np.random.gamma(alpha, mu / alpha, size)
    return np.random.poisson(pois_mu, size)