code: function(filename){
      // resolve by symlink if possible
      for (var from in this.symlinks)
        if (filename.indexOf(from) === 0 && (filename === from || filename[from.length] === '/'))
          return this.symlinks[from] + filename.substr(from.length);
  
      return path.resolve(this.fsBaseURI, filename.replace(/^[\\\/]/, ''));
    }
docs: Returns absolute filesystem filename.
  @param {string} filename
  @return {string}