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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 _get_stddevs_pga(self, C, rup):
 """ Returns the inter- and intra-event coefficients for PGA """

        tau_lnpga_b = self._get_taulny(C, rup.mag)
        phi_lnpga_b = np.sqrt(self._get_philny(C, rup.mag) ** 2. -
                              self.CONSTS["philnAF"] ** 2.)
        return tau_lnpga_b, phi_lnpga_b