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: checkin_time.rb
    path of file: ./repos/onebody/app/models
    
    the code of the file until where you have to start completion: class CheckinTime < ApplicationRecord
  include Concerns::Reor
    
  def to_s
    if the_datetime
      the_datetime.to_s(:full)
    elsif weekday
      "#{Date::DAYNAMES[weekday]} #{time_to_s}"
    else
      '' # invalid time
    end