def _update_Qxy(self):
for w in range(N_NT):<EOL><INDENT>scipy.copyto(self.Qxy, self.phi[w], where=CODON_NT_MUT[w])<EOL><DEDENT>self.Qxy[CODON_TRANSITION] *= self.kappa<EOL>
Update `Qxy` using current `kappa` and `phi`.