With python programming:

Character/letter rotation: construct a function which takes an input string with only letters, automatically apply the following mapping to the string, and return the output:

a --> b b --> c c --> d ... y --> z z --> a 

As an example, if the input is "banana", you should return "cbobob". Note the mapping should apply to both upper and lower cases.

Your solution:

def rotate_characters(input): output = '' ### START YOUR CODE HERE ###

#### END YOUR CODE HERE #### return output