code: def new(options = {})
        raise ArgumentError.new("Creating on a relation requires the parent be saved first.") if @related_object.nil?
  
        id_field = (@related_object.class.to_s.underscore + '_id').to_sym
        new_obj = @klass.new(options.merge(id_field => @related_object.id))
  
        new_obj
      end
docs: task.assignees.new(:name => 'BoB')
   creates a new unsaved Assignee object on the Task object task