input: Write a function to determine if two given strings are anagrams. The function should return True if they are anagrams, otherwise return False. If either of the given strings is empty, return False.
  assert is_anagram("abcd", "cbda")==True
  assert is_anagram("silent", "listen")==True
  assert is_anagram("abc", "def")==False
  assert is_anagram("", "def")==False
  assert is_anagram("abc", "")==False
output: def is_anagram(s1, s2):
      if s1 == "" or s2 == "":
          return False
      return sorted(s1) == sorted(s2)