Python-Cipher_Encryption
A function named encrypt that will be passed two arguments, a string and a dictionary that represents a Caeser cipher that specifies how letter substitutions should be performed. In this cipher, each letter is replaced by the letter three places later in the alphabet, i.e. “a” becomes “d”, “b” turns into “e”, and so on. At the end of the alphabet the cipher “wraps around” so “x” is replaced by “a”. The return value of encrypt function should be a new string where every letter from the input string has been translated according the cipher.