docs: function getResult (obj, prop, file, callback) {
    var value = obj[prop];
  
    if (typeof value === "function") {
      return value.apply(obj, [file, callback]);
    }
  
    if (!callback) {
      // The synchronous plugin functions (canParse and canRead)
      // allow a "shorthand" syntax, where the user can match
      // files by RegExp or by file extension.
      if (value instanceof RegExp) {
        return value.test(file.url);
      }
      else if (typeof value === "string") {
        return value === file.extension;
      }
      else if (Array.isArray(value)) {
        return value.indexOf(file.extension) !== -1;
      }
    }
  
    return value;
  }