input: Write a Python function to determine if two input strings are rotations of one another.
  assert are_rotations("abc", "cba") == False
  assert are_rotations("abcd", "cdba") == False
  assert are_rotations("abacd", "cdaba") == True
output: def are_rotations(str1, str2):
      if len(str1) != len(str2):
          return False
      return str2 in (str1 + str1)