You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: encryption_helper.rb
    path of file: ./repos/gitlabhq/app/models/concerns/token_authenticatable_strategies
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module TokenAuthenticatableStrategies
  class EncryptionHelper
    DYNAMIC_NONCE_IDENTIFIER = "|"
    NONCE_SIZE = 12

    def self.decrypt_token(token)
      return unless token

      # The pattern of the token is "#{DYNAMIC_NONCE_IDENTIFIER}#{token}#{iv_of_12_characters}"
      if token.start_with?(DYNAMIC_NONCE_IDENT
    
    def self.decrypt_token(token)
      return unless token

      # The pattern of the token is "#{DYNAMIC_NONCE_IDENTIFIER}#{token}#{iv_of_12_characters}"
      if token.start_with?(DYNAMIC_NONCE_IDENTIFIER) && token.size > NONCE_SIZE + DYNAMIC_NONCE_IDENTIFIER.size
        token_to_decrypt = token[1...-NONCE_SIZE]
        iv = token[-NONCE_SIZE..]

        Gitlab::CryptoHelper.aes256_gcm_decrypt(token_to_decrypt, nonce: iv)
      else
        Gitlab::CryptoHelper.aes256_gcm_decrypt(token)
      end