ment('div');
    this.$outer.classList.add('toolbox-container');
    this.$container = document.createElement('div');
    this.$container.classList.add('toolbox');
    this.$displayLink = document.createElement('a');
    this.$displayLink.setAttribute('href', '#');
    this.$displayLink.textContent = 'Syntax-Directed Operations';
    this.$displayLink.addEventListener('click', e => {
      e.preventDefault();
      e.stopPropagation();
      referencePane.showSDOs(sdoMap[this.$alternativeId] || {}, this.$al