input: 
  def encrypt_decrypt_string(plaintext: str, action: str) -> str:
      """Encrypt or decrypt the given string using the AES algorithm.
      The action parameter should be either 'encrypt' or 'decrypt'.
      >>> encrypt_decrypt_string('Hello World', 'encrypt')
      b'K\xf7/bV\xee~\x1b\xf3.\xf2xCI\\\xb2'
      >>> encrypt_decrypt_string(b'K\xf7/bV\xee~\x1b\xf3.\xf2xCI\\\xb2', 'decrypt')
      'Hello World'
      """
      
      key = b'Sixteen byte key'
      
      if action == 'encrypt':
          cipher = AES.new(key, AES.MODE_ECB)
          return cipher.encrypt(plaintext.encode())
      elif action == 'decrypt':
          cipher = AES.new(key, AES.MODE_ECB)
          return cipher.decrypt(ciphertext).decode()
  
output:     from Crypto.Cipher import AES
      import base64
  
      if action == 'encrypt':
          cipher = AES.new(key, AES.MODE_ECB)
          padded_plaintext = plaintext.encode() + b'\0' * (AES.block_size - len(plaintext.encode()) % AES.block_size)
          return base64.b64encode(cipher.encrypt(padded_plaintext))
      elif action == 'decrypt':
          cipher = AES.new(key, AES.MODE_ECB)
          decoded_ciphertext = base64.b64decode(plaintext)
          decrypted_text = cipher.decrypt(decoded_ciphertext).rstrip(b'\0')
          return decrypted_text.decode()