input: Write a function to determine if two strings are anagrams of each other. Return True if they are anagrams, otherwise return False. If either string is empty, return False.
  assert is_anagram("abcd", "cbda")==True
  assert is_anagram("abcd", "cdaa")==False
  assert is_anagram("", "cbda")==False
  assert is_anagram("abcd", "")==False
  assert is_anagram("", "")==False
output: def is_anagram(s1, s2):
      if s1 == "" or s2 == "":
          return False
      return sorted(s1) == sorted(s2)