code: function Layer(name, fn) {
    this.length = fn.length;
    this.name = name;
    this.fn = fn;
  }
docs: Representation of a single middleware layer.
  
  @constructor
  @param {String} name Identification of the middleware.
  @param {Function} fn Middleware function.
  @param {Mixed} context Execution context of the function.
  @api private