code: function interfac(options, start, end) {
  
    var go;
    if (end >= 0) {
      go = fs.createReadStream(options.file, {
        flags: options.flag,
        mode: options.mode,
        encoding: options.encoding,
        autoClose: options.autoClose,
        start: start,
        end: end,
        fd: null,
      });
    } else {
      go = fs.createReadStream(options.file, {
        flags: options.flag,
        mode: options.mode,
        encoding: options.encoding,
        autoClose: options.autoClose,
        start: start,
        fd: null,
      });
    }
    return go;
  }
docs: /*
  functions
   
  build stream interface
  
  @function interfac
  @param {Object} options - various options. Check README.md
  @param {Integer} start - starting bytes
  @param {Integer} [end] - ending bytes
  @return {Objetc}