input: Write a function to determine whether two given strings are anagrams. If they are, return True; otherwise, return False. If one of the strings is empty, return False.
  assert is_anagram("abcd", "cbda")==True
  assert is_anagram("hello", "ollhe")==True
  assert is_anagram("python", "typhon")==True
  assert is_anagram("abcd", "abce")==False
  assert is_anagram("abcd", "")==False
output: def is_anagram(s1, s2):
      if s1 == "" or s2 == "":
          return False
      return sorted(s1) == sorted(s2)