function _defaultRouteParser(shim, fn, fnName, route) {
  if (route instanceof RegExp) {
    return '/' + route.source + '/'
  } else if (typeof route === 'string') {
    return route
  }

  return '<unknown>'
}
Default route parser function if one is not provided.

@private
@param {WebFrameworkShim} shim
 The shim in use for this instrumentation.
@param {Function} fn
 The function which received this route string/RegExp.
@param {string} fnName
 The name of the function to which this route was given.
@param {string|RegExp} route
 The route that was given to the function.
 @returns {string} route name
@see RouteParserFunction