getLazyOnceSource(block, dependencies, id, { runtimeTemplate, chunkGraph }) {
		const promise = runtimeTemplate.blockPromise({
			chunkGraph,
			block,
			message: "lazy-once context",
			runtimeRequirements: new Set()
		});
		const arrow = runtimeTemplate.supportsArrowFunction();
		const map = this.getUserRequestMap(dependencies, chunkGraph);
		const fakeMap = this.getFakeMap(dependencies, chunkGraph);
		const thenFunction =
			fakeMap !== 9
				? `${arrow ? "id =>" : "function(id)"} {
		${this.getReturnModuleObjectSource(fakeMap, true)};
	}`
				: RuntimeGlobals.require;

		return `var map = ${JSON.stringify(map, null, "\t")};
${this.getFakeMapInitStatement(fakeMap)}

function webpackAsyncContext(req) {
	return webpackAsyncContextResolve(req).then(${thenFunction});
}
function webpackAsyncContextResolve(req) {
	return ${promise}.then(${arrow ? "() =>" : "function()"} {
		if(!${RuntimeGlobals.hasOwnProperty}(map, req)) {
			var e = new Error("Cannot find module '" + req + "'");
			e.code = 'MODULE_NOT_FOUND';
			throw e;
		}
		return map[req];
	});
}
webpackAsyncContext.keys = ${runtimeTemplate.returningFunction(
			"Object.keys(map)"
		)};
webpackAsyncContext.resolve = webpackAsyncContextResolve;
webpackAsyncContext.id = ${JSON.stringify(id)};
module.exports = webpackAsyncContext;`;
	}
@param {AsyncDependenciesBlock} block block
@param {Dependency[]} dependencies dependencies
@param {ModuleId} id module id
@param {object} options options object
@param {RuntimeTemplate} options.runtimeTemplate the runtime template
@param {ChunkGraph} options.chunkGraph the chunk graph
@returns {string} source code