docs: function(key, done) {
        if(!this._key) {
          done('no key found for metadata');
          return;
        }
        var self = this;
        this._getCollection(function(err) {
          if(err) {
            done(err);
          }
          var kobj = {};
          kobj[self._key.getName()] = key;
          self._collection.find(kobj).toArray(function(err, docs) {
            var ret;
            if(!err && docs.length !== 0) {
              ret = docs[0];
            }
            self._collection.remove(kobj, function(err, result) {
              self._db.close();
              done(err, ret);
            });
          });
        });
      }