function createMinusField(args = undefined) {
  const minus = new Blockly.FieldImage(minusImage, 15, 15, undefined, onClick_);
  /**
   * Untyped args passed to block.minus when the field is clicked.
   * @type {?(Object|undefined)}
   * @private
   */
  minus.args_ = args;
  return minus;
}
Creates a minus image field used for mutation.
@param {Object=} args Untyped args passed to block.minus when the field
    is clicked.
@returns {Blockly.FieldImage} The minus field.