input: Write a function to create an encryption and decryption application in Python. The function should take a string as input and use the AES cipher algorithm in ECB mode for encryption and decryption. Implement the encrypt function to encrypt the given string and the decrypt function to decrypt the given ciphertext.
  
  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'Encryption Test') != b'Encryption Test'
  assert decrypt(encrypt(b'Encryption Test')) == b'Encryption Test'
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)