private HttpRoute determineRoute(final HttpHost target, final HttpRequest request, final HttpContext context) throws HttpException {
        return this.routePlanner.determineRoute(target, request, context);
    }
Internal implementation of {@link CloseableHttpClient}.
<p>
Concurrent message exchanges executed by this client will get assigned to
separate connections leased from the connection pool.
</p>

@since 4.3
httpclient5/src/main/java/org/apache/hc/client5/http/impl/classic/InternalHttpClient.java