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: id_token_builder.rb
    path of file: ./repos/identity-idp/app/services
    
    the code of the file until where you have to start completion: class IdTokenBuilder
  JWT_SIGNING_ALGORITHM = 'RS256'.freeze
  NUM_BYTES_FIRST_128_BITS = 128 / 8

  attr_reader :identity, :now

  def initialize(identity:, code:, custom_expiration: nil, now:
    
  def id_token_claims
    claims = {
      nonce: identity.nonce,
      aud: identity.service_provider,
      jti: SecureRandom.urlsafe_base64,
      at_hash: hash_token(identity.access_token),
      c_hash: hash_token(code),
    }

    if !sp_requests_vot?
      claims[:acr] = acr
    end