In Python

Write a function sanitize () that takes one argument, st, which is a string that is supposed to contain only uppercase letters, lowercase letters and digits (numbers in the form of a string). The function should analyze the string, then separate uppercase letters, lowercase letters and digits into three different result strings. In the end, the function puts these three strings into a single list, and returns the list Note: Please make sure the order of the strings in your final list matches this order: string of uppercase letters, string of lowercase letters, string of digits]