chart = {
const svg = d3.create("svg").attr("viewBox", [0, 0, width, width * 0.7]);
svg
.append("path")
.datum(
topojson.mesh(belgium, belgium.objects.municipalities, (a, b) => a !== b)
)
.attr("fill", "none")
.attr("stroke", "#eeeeee")
.attr("stroke-linejoin", "round")
.attr("d", path);
svg
.append("path")
.datum(topojson.feature(belgium, belgium.objects.provinces))
.attr("stroke", "#cccccc")
.attr("fill-opacity", 0)
.attr("stroke-width", 1)
.attr("stroke-opacity", 1)
.attr("d", path);
svg
.append("g")
.selectAll("path")
.data(rail.features)
.join("path")
.attr("fill", "none")
.attr("stroke", "black")
.attr("fill-opacity", 0)
.attr("stroke-width", 1)
.attr("stroke-opacity", 0.8)
.attr("d", path);
return svg.node();
}