function(data, encoding, callback) {
    if (this.error) {
      if (callback) {
        callback(error);
      }
      throw error;
    } else {
      return this.stream.write(data, encoding, callback);
    }
  }
function(data, encoding, callback) {
    if (this.error) {
      if (callback) {
        callback(error);
      }
      throw error;
    } else {
      return this.stream.write(data, encoding, callback);
    }
  }
function ( data , encoding , callback ) { if ( this . error ) { if ( callback ) { callback ( error ) ; } throw error ; } else { return this . stream . write ( data , encoding , callback ) ; } }
========================================================================== Stream.Writable interface
========================================================================== Stream . Writable interface
Writes the specified data to the file system.