input: Write a python function to check if one string is a permutation of another string.
  assert is_permutation("abc", "bca") == True
  assert is_permutation("abc", "abcd") == False
  assert is_permutation("aabbcc", "bbaacc") == True
  assert is_permutation("xyz", "zyxw") == False
  assert is_permutation("hello", "olleh") == True
output: def is_permutation(str1, str2):
      return sorted(str1) == sorted(str2)