input: 
  from Crypto.Cipher import AES
  
  key = b'Sixteen byte key'
  
  def encrypt(plaintext: str) -> bytes:
      """ Encrypt a given plaintext string using AES encryption in ECB mode.
      >>> encrypt("hello world")
      b'(\xef\x1f\xa7^\xd8$\xbdVb\n\xc3\xf0'
      """
      cipher = AES.new(key, AES.MODE_ECB)
      return cipher.encrypt(plaintext)
  
  def decrypt(ciphertext: bytes) -> str:
      """ Decrypt a given ciphertext using AES decryption in ECB mode.
      >>> decrypt(b'(\xef\x1f\xa7^\xd8$\xbdVb\n\xc3\xf0')
      "hello world"
      """
      cipher = AES.new(key, AES.MODE_ECB)
      return cipher.decrypt(ciphertext)
  
output:     
      cipher = AES.new(key, AES.MODE_ECB)
      decrypted_bytes = cipher.decrypt(ciphertext)
      return decrypted_bytes.decode('utf-8')
  