input: from Crypto.Cipher import AES
  
  key = b'Sixteen byte key'
  
  def encrypt(plaintext):
      """ Encrypts a given plaintext string using AES encryption in ECB mode with a predefined key.
      >>> encrypt(b'Hello, World!')
      b'J/\xe0\xf7I\xe2a\x1fN\xe5R#Qx2G'
      """
      cipher = AES.new(key, AES.MODE_ECB)
      return cipher.encrypt(plaintext)
  
  def decrypt(ciphertext):
      """ Decrypts a given ciphertext string using AES decryption in ECB mode with a predefined key.
      >>> decrypt(b'J/\xe0\xf7I\xe2a\x1fN\xe5R#Qx2G')
      b'Hello, World!'
      """
      cipher = AES.new(key, AES.MODE_ECB)
      return cipher.decrypt(ciphertext)
output:     cipher = AES.new(key, AES.MODE_ECB)
      return cipher.decrypt(ciphertext)