Using a module instead of a class with Virtus

virtus_module.rb

module Entity
  include Virtus.module
  
  attribute :id, Integer

  def persisted?
    !id.nil?
  end
end

class Loan
  include Virtus.model(finalize: false)
  
  include Entity

  attribute :lender, "Person"
  attribute :thing, "Thing"
  attribute :borrower, "Person"
end

class Person
  include Virtus.model(finalize: false)
  
  include Entity

  attribute :name, String
  attribute :email, String
  attribute :loans, Array["Loan"]
end

class Thing
  include Virtus.model
  
  include Entity

  attribute :name, String
  attribute :description, String
end

Virtus.finalize