<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def adev(self, tau0, tau):
 """ return predicted ADEV of noise-type at given tau """

        prefactor = self.adev_from_qd(tau0=tau0, tau=tau)
        c = self.c_avar()
        avar = pow(prefactor, 2)*pow(tau, c)
        return np.sqrt(avar)