input: Write a python function to check if two strings are anagrams. 
  assert is_anagram("listen", "silent") == True 
  assert is_anagram("hello", "billion") == False 
  assert is_anagram("Dormitory", "Dirty room") == True 
  assert is_anagram("School master", "The classroom") == True
output: def is_anagram(str1, str2):
      str1 = ''.join(str1.split()).lower()
      str2 = ''.join(str2.split()).lower()
      return sorted(str1) == sorted(str2)