input: Write a function called is_anagram that takes two strings str1 and str2 and returns True if they are anagrams of each other, otherwise returns False. If either of the strings is empty, return True.
  assert is_anagram("abcd", "cbda")==True
  assert is_anagram("abc", "def")==False
  assert is_anagram("listen", "silent")==True
  assert is_anagram("hello", "world")==False
  assert is_anagram("", "")==True
output: def is_anagram(str1, str2):
      if str1 == "" or str2 == "":
          return True
      return sorted(str1) == sorted(str2)