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: shipping_rate.rb
    path of file: ./repos/spree/core/app/models/spree
    
    the code of the file until where you have to start completion: module Spree
  class ShippingRate < Spree::Base
    belongs_to :shipment, class_name: 'Spree::Shipment'
    belongs_to :tax_rate, -> { with_deleted }, class_name: 'Spree::TaxRate'
    belongs_to :shipping_method, -> { with_deleted }, class_name: 'Spre
    
    def display_price
      price = display_base_price.to_s

      return price if tax_rate.nil? || tax_amount.zero?

      Spree.t(
        tax_rate.included_in_price? ? :including_tax : :excluding_tax,
        scope: 'shipping_rates.display_price',
        price: price,
        tax_amount: display_tax_amount,
        tax_rate_name: tax_rate.name
      )
    end