grouped_records

# File activerecord/lib/active_record/associations/preloader.rb, line 155
        def grouped_records(association, records, polymorphic_parent)
          h = {}
          records.each do |record|
            reflection = record.class._reflect_on_association(association)
            next if polymorphic_parent && !reflection || !record.association(association).klass
            (h[reflection] ||= []) << record
          end
          h
        end