(2) Write a function trans(M) which returns the transpose of an n-by-n matrix M. The matrix M is represented by a list of n lists, each of length n. Transposing M means that each M[i][j] is swapped (once!) with M[j][i].
The function must not use print(..) nor input(..). Write your own functions { don't call readymade solutions.
Example: trans([[4,2,1], ['a','a','a'], [-1,-2,-3]]) should return [[4,'a',-1], [2,'a',-2], [1,'a',-3]].