input: Write a function to determine if two given strings are anagrams of each other. If they are anagrams return True else return False. If both strings are empty then return True.  
  assert is_anagram("abcd", "cbda")==True  
  assert is_anagram("hello", "world")==False  
  assert is_anagram("cinema", "iceman")==True  
  assert is_anagram("", "")==True
output: def is_anagram(s1, s2):
      return sorted(s1) == sorted(s2)