code: function collections(db, options, callback) {
    let Collection = loadCollection();
  
    options = Object.assign({}, options, { nameOnly: true });
    // Let's get the collection names
    db.listCollections({}, options).toArray((err, documents) => {
      if (err != null) return handleCallback(callback, err, null);
      // Filter collections removing any illegal ones
      documents = documents.filter(doc => {
        return doc.name.indexOf('$') === -1;
      });
  
      // Return the collection objects
      handleCallback(
        callback,
        null,
        documents.map(d => {
          return new Collection(
            db,
            db.s.topology,
            db.s.databaseName,
            d.name,
            db.s.pkFactory,
            db.s.options
          );
        })
      );
    });
  }
docs: Fetch all collections for the current db.
  
  @method
  @param {Db} db The Db instance on which to fetch collections.
  @param {object} [options] Optional settings. See Db.prototype.collections for a list of options.
  @param {Db~collectionsResultCallback} [callback] The results callback