How to use the core-js/features/object.assign function in core-js

function copyRestangularizedElement(fromElement, toElement = {}) {
        const copiedElement = assign(toElement, fromElement);
        return restangularizeElem(copiedElement[config.restangularFields.parentResource],
          copiedElement, copiedElement[config.restangularFields.route], true);
      }

static createRequestQueryParams(queryParams) {
    const requestQueryParams = assign({}, queryParams);
    let search: HttpParams = new HttpParams();

    for (const key in requestQueryParams) {
      let value: any = requestQueryParams[key];

      if (Array.isArray(value)) {
        value.forEach(function (val) {
          search = search.append(key, val);
        });
      } else {
        if (typeof value === 'object') {
          value = JSON.stringify(value);
        }
        search = search.append(key, value);
      }
    }

static createRequestHeaders(headers) {
    for (const key in headers) {
      const value: any = headers[key];
      if (typeof value === 'undefined') {
        delete headers[key];
      }
    }

    return new HttpHeaders(assign({}, headers));
  }
}

constructor(
    @Optional() @Inject(RESTANGULAR) public configObj,
    private injector: Injector,
    private http: RestangularHttp
  ) {
    this.provider = new providerConfig(http);
    const element = this.provider.$get();
    assign(this, element);

    this.setDefaultConfig();
  }