code: def encipher_shift(plaintext, plain_vocab, shift):
      """Encrypt plain text with a single shift layer.
  
      Args:
        plaintext (list of list of Strings): a list of plain text to encrypt.
        plain_vocab (list of Integer): unique vocabularies being used.
        shift (Integer): number of shift, shift to the right if shift is positive.
      Returns:
        ciphertext (list of Strings): encrypted plain text.
      """
      ciphertext = []
      cipher = ShiftEncryptionLayer(plain_vocab, shift)
  
      for _, sentence in enumerate(plaintext):
          cipher_sentence = []
          for _, character in enumerate(sentence):
              encrypted_char = cipher.encrypt_character(character)
              cipher_sentence.append(encrypted_char)
          ciphertext.append(cipher_sentence)
  
      return ciphertext
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from collections import deque
  import numpy
  from tensor2tensor.data_generators import algorithmic
  from tensor2tensor.utils import registry
label_desc: Use image node_id 2 for calling a global function with example usage: encipher_shift(plaintext, plain_vocab, shift) and returns: ciphertext