-----Description-----
This task requires writing a Lean 4 method that determines if a given string is a palindrome, ignoring all
non-alphanumeric characters and case differences. For example, the string "A man, a plan, a canal: Panama" should return
true.

-----Input-----
A single string:
s: The string to check for palindrome property.

-----Output-----
A boolean (Bool):
true if s is a palindrome when ignoring non-alphanumeric characters and case. false otherwise.

