input: Write a function to encrypt and decrypt strings using AES encryption in Python. The function should take a plaintext string as input and return the encrypted ciphertext. The function should also have the ability to take a ciphertext as input and return the decrypted plaintext string. Use ECB mode for the AES encryption.
  
  
  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'
  
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)