code: function selectBox(selection, label) {
    selection
        .classed('form-group', true)
        .classed('form-row', true)
        .classed('align-items-center', true);
    selection.append('label')
        .classed('col-form-label', true)
        .classed('col-form-label-sm', true)
        .classed('col-4', true)
        .text(label);
    selection.append('select')
        .classed('form-control', true)
        .classed('form-control-sm', true)
        .classed('col-8', true)
        .on('input', function () {
          const valid = box.formValid(selection);
          selection.call(box.setValidity, valid);
        });
  }
docs: Render select box components
  @param {d3.selection} selection - selection of box container (div element)