How to use the @opentelemetry/core.isValid function in @opentelemetry/core

startSpan(name: string, options: types.SpanOptions = {}): types.Span {
    const parentContext = this._getParentSpanContext(options.parent);
    // make sampling decision
    const samplingDecision = this._sampler.shouldSample(parentContext);
    const spanId = randomSpanId();
    let traceId;
    let traceState;
    if (!parentContext || !isValid(parentContext)) {
      // New root span.
      traceId = randomTraceId();
    } else {
      // New child span.
      traceId = parentContext.traceId;
      traceState = parentContext.traceState;
    }
    const traceFlags = samplingDecision
      ? TraceFlags.SAMPLED
      : TraceFlags.UNSAMPLED;
    const spanContext = { traceId, spanId, traceFlags, traceState };
    const recordEvents = options.isRecording || false;
    if (!recordEvents && !samplingDecision) {
      this.logger.debug('Sampling is off, starting no recording span');
      return new NoRecordingSpan(spanContext);
    }

const method = request.method || 'GET';

      plugin._logger.debug('%s plugin incomingRequest', plugin.moduleName);

      if (Utils.isIgnored(pathname, plugin._config.ignoreIncomingPaths)) {
        return original.apply(this, [event, ...args]);
      }

      const propagation = plugin._tracer.getHttpTextFormat();
      const headers = request.headers;
      const spanOptions: SpanOptions = {
        kind: SpanKind.SERVER,
      };

      const spanContext = propagation.extract(Format.HTTP, headers);
      if (spanContext && isValid(spanContext)) {
        spanOptions.parent = spanContext;
      }

      const span = plugin._startHttpSpan(`${method} ${pathname}`, spanOptions);

      return plugin._tracer.withSpan(span, () => {
        plugin._tracer.bind(request);
        plugin._tracer.bind(response);

        // Wraps end (inspired by:
        // https://github.com/GoogleCloudPlatform/cloud-trace-nodejs/blob/master/src/plugins/plugin-connect.ts#L75)
        const originalEnd = response.end;
        response.end = function(
          this: ServerResponse,
          ...args: ResponseEndArgs
        ) {