Write a Python function to check whether a string is a palindrome or not

def is_palindrome(s):

    s = ''.join(char.lower() for char in s if char.isalnum())

    return s == s[::-1]

print(is_palindrome("level"))

print(is_palindrome("radar"))

print(is_palindrome("tenet"))

print(is_palindrome("Tanishk"))