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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 tls_session_update(self, msg_str):
 """ Covers both post_build- and post_dissection- context updates. """

        self.tls_session.handshake_messages.append(msg_str)
        self.tls_session.handshake_messages_parsed.append(self)