lib/output.js
function _updateFormatOut (formatOut, options) {
  if (!(is.object(options) && options.force === false)) {
    this.options.formatOut = formatOut;
  }
  return this;
}
function _updateFormatOut (formatOut, options) {
  if (!(is.object(options) && options.force === false)) {
    this.options.formatOut = formatOut;
  }
  return this;
}
function _updateFormatOut ( formatOut , options ) { if ( ! ( is . object ( options ) && options . force === false ) ) { this . options . formatOut = formatOut ; } return this ; }
Update the output format unless options.force is false,
in which case revert to input format.
@private
@param {String} formatOut
@param {Object} [options]
@param {Boolean} [options.force=true] - force output format, otherwise attempt to use input format
@returns {Sharp}
Update the output format unless options . force is false in which case revert to input format .