Given two strings s and t, create a function to determine if they are isomorphic. Two strings are isomorphic if the characters in s can be replaced to get t. All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.
is_isomorphic("egg", "add") ➞ True
is_isomorphic("aba", "baa") ➞ False
is_isomorphic("paper", "title") ➞ True
N/A