code: function(options) {
          var extraClass = options.dropdownCssClass ? ' ' + options.dropdownCssClass : '',
              searchInput = '';
          if (options.showSearchInput) {
              extraClass += ' has-search-input';
  
              var placeholder = options.searchInputPlaceholder;
              searchInput =
                  '<div class="selectivity-search-input-container">' +
                  '<input type="text" class="selectivity-search-input"' +
                  (placeholder ? ' placeholder="' + escape(placeholder) + '"' : '') +
                  '>' +
                  '</div>';
          }
          return (
              '<div class="selectivity-dropdown' +
              extraClass +
              '">' +
              searchInput +
              '<div class="selectivity-results-container"></div>' +
              '</div>'
          );
      }
docs: Renders the dropdown.
  
  The template is expected to have at least one element with the class
  'selectivity-results-container', which is where all results will be added to.
  
  @param options Options object containing the following properties:
  dropdownCssClass - Optional CSS class to add to the top-level element.
  searchInputPlaceholder - Optional placeholder text to display in the search
  input in the dropdown.
  showSearchInput - Boolean whether a search input should be shown. If true,
  an input element with the 'selectivity-search-input' is
  expected.