polymorphic?

# File activerecord/lib/active_record/associations/preloader/branch.rb, line 102
        def polymorphic?
          return false if root?
          return @polymorphic if defined?(@polymorphic)

          @polymorphic = source_records.any? do |record|
            reflection = record.class._reflect_on_association(association)
            reflection && reflection.options[:polymorphic]
          end
        end