How to use the fabric-ca-client/lib/FabricCAServices.addConfigFile function in fabric-ca-client

function getFabricCAService() {
	FabricCAServices.addConfigFile(path.join(__dirname, 'e2e', 'config.json'));
	ORGS = FabricCAServices.getConfigSetting('test-network');
	fabricCAEndpoint = ORGS[userOrg].ca.url;

	FabricCAServices.getConfigSetting('crypto-keysize', '256');// force for npm test
	FabricCAServices.setConfigSetting('crypto-hash-algo', 'SHA2');// force for npm test

	return new FabricCAServices(fabricCAEndpoint, tlsOptions, ORGS[userOrg].ca.name);
}