appendControls() {
    const fragment = document.createDocumentFragment()
    empty(this.dom)
    // append controls to list
    this.orderFields(this.controlList).forEach(controlKey => {
      const control = this.allControls[controlKey]
      if (control) {
        fragment.appendChild(control)
      }
    })
    this.dom.appendChild(fragment)
  }
Adds the controls to the control list