code: function gridform (options) {
    options || (options = {});
  
    var db = options.db || (options.db = exports.db);
    if (!db) throw new Error('missing db');
    delete options.db;
  
    var mongo = options.mongo || (options.mongo = exports.mongo);
    if (!mongo) throw new Error('missing mongodb native driver');
    delete options.mongo;
  
    var filename = options.filename || (options.filename = exports.filename || ƒ);
    delete options.filename;
  
    var form = new formidable.IncomingForm;
    form.__gridstream = gridstream(db, mongo);
    form.__filename = filename;
    form.onPart = onPart;
    return form;
  }
docs: gridform
  
  @param {Object} options
  @return {formidable.IncomingForm}