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