Vectortile only supports XYZ tile coordinate initialization and does not support bbox initialization

[ligai322]

node-mapnik only one way initialization mapnik.Vectortile,like this:
var vtile = new mapnik.VectorTile(16,33275,22518);

the params is tile coordinates(z,x,y).It Cannot initialize by extent, like :

var vtile = new mapnik.VectorTile(bbox);

But mapnik-vector-tile has two ways to initialization the VectorTile.

Because I'm not using Google tiles scheme for create vectortile.

Do you have any plans to add interfaces initialized by extent?