The set L is defined as the set of all strings x$,$ where x is a string composed of the characters $\text{'}$a$\text{'}$ and $\text{'}$b$\text{'},$ and x either does not contain the substring $\text{'}$bb$\text{'},$ or the number of $\text{'}$b$\text{'}$s in x $($denoted as nb$($x$))$ is even.