input: Write a function to check if two given strings are anagrams. An anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once. If the strings are anagrams, return True, otherwise return False. Return True if both strings are empty.
  
  assert is_anagram("abcd", "cbda")==True
  assert is_anagram("abcd", "abc")==False
  assert is_anagram("listen", "silent")==True
  assert is_anagram("python", "typhon")==True
  assert is_anagram("", "")==True
output: def is_anagram(s1, s2):
      return sorted(s1) == sorted(s2)