How to use the lsif-protocol.VertexLabels.document function in lsif-protocol

interface VisEdge {
	from: number;
	to: number;
	label: string;
}

interface VisData {
	nodes: VisNode[];
	edges: VisEdge[];
}

function baseName(uri: string): string {
	return path.basename(URI.parse(uri).fsPath);
}

const include: Set = new Set([VertexLabels.document, VertexLabels.range, VertexLabels.resultSet, VertexLabels.referenceResult]);
function filterVertex(element: Vertex): boolean {
	return !include.has(element.label);
}

export const create: Create = (writer: Writer): Emitter => {
	let data: VisData = {
		nodes: [],
		edges: []
	};
	return {
		start: () => {

		},
		emit: (element: Vertex | Edge) => {
			if (element.type === 'vertex') {
				if (filterVertex(element)) {

private processVertex(vertex: Vertex): void {
		this.vertices.all.set(vertex.id, vertex);
		switch(vertex.label) {
			case VertexLabels.metaData:
				this.version = vertex.version;
				if (vertex.projectRoot !== undefined) {
					this.projectRoot = URI.parse(vertex.projectRoot);
				}
				break;
			case VertexLabels.project:
				this.vertices.projects.set(vertex.id, vertex);
				break;
			case VertexLabels.document:
				this.vertices.documents.set(vertex.id, vertex);
				this.indices.documents.set(vertex.uri, vertex);
				break;
			case VertexLabels.range:
				this.vertices.ranges.set(vertex.id, vertex);
				break;
		}
	}

public insert(element: Edge | Vertex): void {
		if (element.type === ElementTypes.vertex) {
			switch (element.label) {
				case VertexLabels.metaData:
					this.insertMetaData(element);
					break;
				case VertexLabels.project:
					this.insertProject(element);
					break;
				case VertexLabels.document:
					this.insertDocument(element);
					break;
				case VertexLabels.packageInformation:
					this.insertPackageInformation(element);
					break;
				case VertexLabels.range:
					this.insertRange(element);
					break;
				default:
					this.insertVertex(element);
			}
		} else {
			switch(element.label) {
				case EdgeLabels.contains:
					this.insertContains(element);
					break;

public insert(element: Edge | Vertex): void {
		if (element.type === ElementTypes.vertex) {
			switch(element.label) {
				case VertexLabels.metaData:
					this.handleMetaData(element);
					break;
				case VertexLabels.document:
					this.documents.set(element.id, element);
					break;
				case VertexLabels.range:
					this.handleRange(element);
					break;
				case VertexLabels.resultSet:
					this.handleResultSet(element);
					break;
				case VertexLabels.moniker:
					this.handleMoniker(element);
					break;
				case VertexLabels.hoverResult:
					this.handleHover(element);
					break;
				case VertexLabels.declarationResult:
					this.handleDeclarationResult(element);