input: Write a python function to check if two strings are anagrams.
  assert is_anagram("listen", "silent") == True
  assert is_anagram("hello", "world") == False
  assert is_anagram("schoolmaster", "the classroom") == True
  assert is_anagram("anagram", "nag a ram") == True
output: def is_anagram(s1, s2):
      s1_cleaned = ''.join(s1.split()).lower()
      s2_cleaned = ''.join(s2.split()).lower()
      return sorted(s1_cleaned) == sorted(s2_cleaned)