docs: function(field, val){
              if (2 == arguments.length) {
                  if (Array.isArray(val)) val = val.map(String);
                  else val = String(val);
                  this.res.setHeader(field, val);
              } else {
                  for (var key in field) {
                      this.set(key, field[key]);
                  }
              }
          }