How to use the graphology-utils/is-graph function in graphology-utils

constructor(graph, container, settings) {
    super();

    settings = settings || {};

    this.settings = assign({}, DEFAULT_SETTINGS, settings);

    // Validating
    if (!isGraph(graph))
      throw new Error('sigma/renderers/webgl: invalid graph instance.');

    if (!(container instanceof HTMLElement))
      throw new Error('sigma/renderers/webgl: container should be an html element.');

    // Properties
    this.graph = graph;
    this.captors = {};
    this.container = container;
    this.elements = {};
    this.contexts = {};
    this.listeners = {};

    // Indices & cache
    // TODO: this could be improved by key => index => floatArray
    // TODO: the cache should erase keys on node delete & add new

constructor(graph, renderer) {

    // Checking the arguments
    if (!isGraph(graph))
      throw new Error('Sigma.constructor: given graph is not an instance of a graphology implementation.');

    if (!(renderer instanceof Renderer))
      throw new Error('Sigma.constructor: given renderer is not an instance of a sigma Renderer.');

    // Properties
    this.graph = graph;
    this.renderer = renderer;
    this.renderer.bind(this);

    // Userland state
    this.state = {};
    this.nodeStates = null;
    this.edgeStates = null;

    // First time render