(Python)

I actually do not understand what unicode is. So, could you please explain your solution step by step, thanks.

Write a program that implements a Caesar cipher (rotation cipher), which is a simple system of encoding strings by shifting every letter forward by a given number. Your program should prompt the user to type a message and an encoding "key" (number of places to shift each character) and display the shifted (uppercase) message. For example, if the shift amount is 3, then the letter A becomes D, and B becomes E, and so on. Letters near the end of the alphabet wrap around for a shift of 3, X becomes A, and Y becomes B, and Z becomes C. Sample runs below show the user input in red. Useful functions: - ord( ch): takes a single character as a parameter and returns an integer representing Unicode code point for the given Unicode character. Ex: ord ('a') returns 97. chr( val ): takes an integer value as a parameter and returns a single character (string) whose Unicode code point is the integer. Ex: chr( 97 ) returns 'a'. Sample Run 1: Sample Run 1: Your message? abc defgh xyz. Encoding key? 3 DEF GHIJK ABC. Your message? def ghijk abc. Encoding key? -3 ABC DEFGH XYZ. Sample Run 3: Sample Run 4: Your message? laabbcc 2defgaaa xyzbbxyz! Your message? def ghijk abc. Encoding key? -3 ABC DEFGH XYZ. Encoding key? 4 1EEFFGG 2HIJKEEE BCDFFBCD