input: Write a function to determine if a given string is a valid palindrome considering only alphanumeric characters and ignoring cases. If it is a valid palindrome return True else return False.
  assert is_valid_palindrome("A man, a plan, a canal: Panama")==True
  assert is_valid_palindrome("race a car")==False
  assert is_valid_palindrome("No lemon, no melon")==True
  assert is_valid_palindrome("12321")==True
  assert is_valid_palindrome("")==True
output: def is_valid_palindrome(s: str) -> bool:
      cleaned_s = ''.join(char.lower() for char in s if char.isalnum())
      return cleaned_s == cleaned_s[::-1]