code: function(queries) {
          var queryJSON = _.map(queries, function(q) {
            return q.toJSON().where;
          });
  
          this._where.$and = queryJSON;
          return this;
        }
docs: Add constraint that both of the passed in queries matches.
  @param {Array} queries
  @return {AV.Query} Returns the query, so you can chain this call.
  @private