input: Write a function to create an application in Python for encryption and decryption of strings using the AES algorithm. The application should take a string as input, and use a cipher text algorithm of choice to encrypt the string.
  
  from Crypto.Cipher import AES
  
  key = b'Sixteen byte key'
  
  def encrypt(plaintext):
      cipher = AES.new(key, AES.MODE_ECB)
      return cipher.encrypt(plaintext)
  
  def decrypt(ciphertext):
      cipher = AES.new(key, AES.MODE_ECB)
      return cipher.decrypt(ciphertext)
  
  assert encrypt(b'Hello World') != b'Hello World'
  assert decrypt(encrypt(b'Hello World')) == b'Hello World'
  assert encrypt(b'') == b''
  assert decrypt(encrypt(b'')) == b''
output: def encrypt(plaintext):
      cipher = AES.new(key, AES.MODE_ECB)
      return cipher.encrypt(plaintext)
  
  def decrypt(ciphertext):
      cipher = AES.new(key, AES.MODE_ECB)
      return cipher.decrypt(ciphertext)