Ciphers key and IV are updated accordingly.

def compute_tls13_next_traffic_secrets(self):
        """
        Ciphers key and IV are updated accordingly.
        """
        hkdf = self.prcs.hkdf
        hl = hkdf.hash.digest_size

        cts = self.tls13_derived_secrets["client_traffic_secrets"]
        ctsN = cts[-1]
        ctsN_1 = hkdf.expand_label(ctsN, "application traffic secret", "", hl)
        cts.append(ctsN_1)

        stsN_1 = hkdf.expand_label(ctsN, "application traffic secret", "", hl)
        cts.append(stsN_1)

        if self.connection_end == "server":
            self.prcs.tls13_derive_keys(ctsN_1)
            self.pwcs.tls13_derive_keys(stsN_1)
        elif self.connection_end == "client":
            self.pwcs.tls13_derive_keys(ctsN_1)
            self.prcs.tls13_derive_keys(stsN_1)