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", "bcd") == False
  assert is_permutation("aabbcc", "baccab") == True
  assert is_permutation("abcd", "dcba") == True
  assert is_permutation("abc", "abcd") == False
output: def is_permutation(str1, str2):
      if len(str1) != len(str2):
          return False
      return sorted(str1) == sorted(str2)