geoPath () {
        return this._geoPath;
    }
Returns the {@link https://github.com/d3/d3-geo/blob/master/README.md#paths d3.geoPath} object used to
render the projection and features.  Can be useful for figuring out the bounding box of the
feature set and thus a way to calculate scale and translation for the projection.
@see {@link https://github.com/d3/d3-geo/blob/master/README.md#paths d3.geoPath}
@returns {d3.geoPath}