tmsh command is equivalent to config command on F5.

def tmsh_mode(self, delay_factor=1):
        """tmsh command is equivalent to config command on F5."""
        delay_factor = self.select_delay_factor(delay_factor)
        self.clear_buffer()
        command = "{}tmsh{}".format(self.RETURN, self.RETURN)
        self.write_channel(command)
        time.sleep(1 * delay_factor)
        self.clear_buffer()
        return None