docs: function GFSupload(mongoinst, prefix) {
    this.mongo = mongoinst;
    this.db = this.mongo.db;
    this.Grid = this.mongo.Grid;
    this.GridStore = this.mongo.GridStore;
    this.ObjectID = this.mongo.ObjectID;
    this.prefix = prefix || this.GridStore.DEFAULT_ROOT_COLLECTION;
    return this;
  }