Please use python program

Part I: The Up/Down Cipher: Encryption Algorithm (20 points) Write a function updown encrypt that takes the following arguments, in this order: plaintext: a plaintext string containing letters, digits and spaces that will be encrypted num.rows: the number of rows that will be used in the encryption process Here's how the up/down cipher works. First, take a plaintext string and start drawing characters from it, placing the first num.rows of characters into the first column of a grid from up to down. We assume here that the grid has num.rows rows in it. Then take the next num rows characters, placing them into the second column of the grid in reverse order, from down to up. Continue in this fashion, drawing characters from the plaintext string until you