<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def rweibull(alpha, beta, size=None):
 """ Weibull random variates. """

    tmp = -np.log(runiform(0, 1, size))
    return beta * (tmp ** (1. / alpha))