code: def create_session(self, username, prekeybundle, autotrust=False):
          
          logger.debug("create_session(username=%s, prekeybunder=[omitted], autotrust=%s)" % (username, autotrust))
          session_builder = SessionBuilder(self._store, self._store, self._store, self._store, username, 1)
          try:
              session_builder.processPreKeyBundle(prekeybundle)
          except UntrustedIdentityException as ex:
              if autotrust:
                  self.trust_identity(ex.getName(), ex.getIdentityKey())
              else:
                  raise exceptions.UntrustedIdentityException(ex.getName(), ex.getIdentityKey())
docs: :param username:
          :type username: str
          :param prekeybundle:
          :type prekeybundle: PreKeyBundle
          :return:
          :rtype: