Not print undefined of toDot function (#906)

Author: ishii-norimi

lib/model/nns/graph.js

@@ -121,7 +121,8 @@ export default class ComputationalGraph {
 		let s = 'digraph g {\n'
 		for (let i = 0; i < this._nodes.length; i++) {
 			const node = this.nodes[i]
-			s += `  l${i} [label="${node.layer.constructor.name}\\n${node.name}"];\n`
+			const label = node.layer.constructor.name + (node.name ? `\\n${node.name}` : '')
+			s += `  l${i} [label="${label}"];\n`
 			for (const parent of node.parents) {
 				s += `  l${parent.index} -> l${i};\n`
 			}

tests/lib/model/nns/graph.test.js

@@ -158,9 +158,9 @@ describe('Computational Graph', () => {
 	test('toDot', () => {
 		const graph = new ComputationalGraph()
 		graph.add(Layer.fromObject({ type: 'input' }))
-		graph.add(Layer.fromObject({ type: 'tanh' }))
+		graph.add(Layer.fromObject({ type: 'tanh' }), 't')
 		expect(graph.toDot()).toBe(
-			'digraph g {\n  l0 [label="InputLayer\\nundefined"];\n  l1 [label="TanhLayer\\nundefined"];\n  l0 -> l1;\n}'
+			'digraph g {\n  l0 [label="InputLayer"];\n  l1 [label="TanhLayer\\nt"];\n  l0 -> l1;\n}'
 		)
 	})