input: from Crypto.Cipher import AES
  
  key = b'Sixteen byte key'
  
  def encrypt_decrypt_string(plaintext: str) -> str:
      """Encrypts and then decrypts a given string using AES encryption in ECB mode.
      The function should return the decrypted string, which should be the same as the input string.
      >>> encrypt_decrypt_string('Hello, World!')
      'Hello, World!'
      >>> encrypt_decrypt_string('')
      ''
      >>> encrypt_decrypt_string('Secret Message 123')
      'Secret Message 123'
      """
      cipher = AES.new(key, AES.MODE_ECB)
      ciphertext = cipher.encrypt(plaintext.encode())
      decrypted_text = cipher.decrypt(ciphertext).decode()
      return decrypted_text
output:     cipher = AES.new(key, AES.MODE_ECB)
      padded_plaintext = plaintext + (AES.block_size - len(plaintext) % AES.block_size) * chr(AES.block_size - len(plaintext) % AES.block_size)
      ciphertext = cipher.encrypt(padded_plaintext.encode())
      decrypted_text = cipher.decrypt(ciphertext).decode()
      unpadded_text = decrypted_text[:-ord(decrypted_text[-1])]
      return unpadded_text