List language$($string input, int k$).$ You will see a lot about languages when you study Computational Models. Just think of the input string

$1$

as a set of characters $\backslash$Sigma $($formally called an alphabet$).$ The language generated

by $\backslash$Sigma is the set of all strings comprising of characters $($symbols$)$ in $\backslash$Sigma $.$ This

function generates a list of all strings in the language, whose length is at most

k$.$ Note that empty string is also part of the language. The order of the list

does not matter. For example, if the input is $$abc$$ and k $=2,$ then the output

list has the following strings: $($the empty string$),$ a$,$ b$,$ c$,$ aa$,$ bb$,$ cc$,$ ab$,$ ac$,$ ba$,$

bc$,$ ca$,$ cb$.$ You can assume that input does not have repeated characters