This is the correct version of how to override an attr_accessor in a module in Rails

attendable.rb (correct)

# Concern to be included into an ActiveModel
module Attendable
  extend ActiveSupport::Concern
  
  included do
    attr_reader :user_fees
   end
 
  def user_fees= new_user_fees
    …
    @user_fees = new_user_fees
  end
end