static getClass(type, subtype) {
    const lookup = subtype ? type + '.' + subtype : type
    const controlClass = control.classRegister[lookup] || control.classRegister[type]
    if (!controlClass) {
      return control.error(
        'Invalid control type. (Type: ' +
          type +
          ', Subtype: ' +
          subtype +
          '). Please ensure you have registered it, and imported it correctly.',
      )
    }

    // set the _type field on the control class so we never lose it
    return controlClass
  }
Retrieve the class for a specified control type
@param {String} type type of control we are looking up
@param {String} [subtype] if specified we'll try to find
a class mapped to this subtype. If none found, fall back to the type.
@return {Class} control subclass as defined in the call to register