init() {
    // Create the label.
    this.label = document.createElement('label');
    // Set the name.
    this.label.textContent = this.toolboxItemDef_['name'];
    // Set the color.
    this.label.style.color = this.toolboxItemDef_['colour'];
    // Any attributes that begin with css- will get added to a cssconfig.
    const cssConfig = this.toolboxItemDef_['cssconfig'];
    // Add the class.
    if (cssConfig) {
      this.label.classList.add(cssConfig['label']);
    }
  }
Init method for the label.
@override