input: Write a function to check if two given strings are anagrams. If they are anagrams, return True; otherwise, return False. Two strings are anagrams if they contain the same characters in the same frequency, regardless of the order.
  
  assert is_anagram("abcd", "cbda")==True
  assert is_anagram("hello", "world")==False
  assert is_anagram("abc", "cab")==True
  assert is_anagram("anagram", "nagaram")==True
  assert is_anagram("rat", "car")==False
output: def is_anagram(s1, s2):
      return sorted(s1) == sorted(s2)