code: function calculateBoundsForGeometryCollection(geometryCollection){
      var extents = [], extent;
  
      for (var i = geometryCollection.geometries.length - 1; i >= 0; i--) {
        extent = calculateBounds(geometryCollection.geometries[i]);
        extents.push([extent[0],extent[1]]);
        extents.push([extent[2],extent[3]]);
      }
  
      return calculateBoundsFromArray(extents);
    }
docs: /*
  Internal: Calculate an bounding box for a geometry collection