static fromJson(options) {
    // `this` might be a subclass of FieldPitch if that class doesn't
    // override the static fromJson method.
    return new this(options['pitch']);
  }
Construct a FieldPitch from a JSON arg object.
@param {!Object} options A JSON object with options (pitch).
@returns {!FieldPitch} The new field instance.
@package
@nocollapse