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: school_calendar_step.rb
    path of file: ./repos/i-diario/app/models
    
    the code of the file until where you have to start completion: class SchoolCalendarStep < ActiveRecord::Base
  include SchoolTermable

  acts_as_copy_target

  audited associated_with: :school_calen
    
  def end_at_must_not_have_conflicting_date
    school_calendars = SchoolCalendar.by_unity_id(unity).where.not(id: school_calendar_id)

    exist_conflicting_steps = school_calendars.any? { |school_calendar|
      school_calendar.school_day?(end_at)
    }

    errors.add(:end_at, :must_not_have_conflicting_steps) if exist_conflicting_steps
  end