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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 integral_scale(u, t, tau1=0.0, tau2=1.0):

 """Calculate the integral scale of a time series by integrating up to
 the first zero crossing.
 """

    tau, rho = autocorr_coeff(u, t, tau1, tau2)
    zero_cross_ind = np.where(np.diff(np.sign(rho)))[0][0]
    int_scale = np.trapz(rho[:zero_cross_ind], tau[:zero_cross_ind])
    return int_scale