Convert the following TG M$1$ into an equivalent regular expression $\backslash ($ r $\backslash )$ using the method discussed in class. Do not construct a regular expression directly from the language accepted by M$1.$

M$1$: $\backslash (\backslash$square $\backslash )$

You may use $\text{'}$L$\text{'}$ to mean lambda or you may explicitly declare your lambda symbol at the beginning of your answer.