anchor.diff:     * restrictive queries.
      */
     Query endAt({int priority, String name}) =>
  -      new Query.fromJsObject(_fb.callMethod('endAt', _removeNulls([priority, name])));
  +      new Query.fromJsObject(_fb.callMethod('endAt', _removeTrailingNulls([priority, name])));
   
     /**
      * Queries are attached to a location in your Firebase. This method will
  
positive.code:    * The unique name generated by push() is prefixed with a client-generated
     * timestamp so that the resulting list will be chronologically sorted.
     */
     Firebase push({value}) => new Firebase.fromJsObject(_fb.callMethod('push', _removeNulls([value])));
  
     /**
      * Write data to a Firebase location, like set(), but also specify the
  
negative.code: 
    /**
     * Get a Firebase reference for a location at the specified relative path.
     *
     * The relative path can either be a simple child name, (e.g. 'fred') or a
     * deeper slash seperated path (e.g. 'fred/name/first').
     */
  