Complete the function/method so that it takes a PascalCase string and returns the string in snake_case notation. Lowercase characters can be numbers. If the method gets a number as input, it should return a string.
Your task is to create a function that will take an integer and return the result of the look-and-say function on that integer. This should be a general function that takes as input any positive integer, and returns an integer; inputs are not limited to the sequence which starts with "1".
Write a function named first_non_repeating_letter† that takes a string input, and returns the first character that is not repeated anywhere in the string.