@Override
        public boolean isConnected() {
            final PoolEntry<HttpRoute, ManagedHttpClientConnection> poolEntry = getPoolEntry();
            final ManagedHttpClientConnection connection = poolEntry.getConnection();
            return connection != null && connection.isOpen();
        }
Defines period of inactivity after which persistent connections must
be re-validated prior to being {@link #lease(String, HttpRoute, Object)} leased} to the consumer.
Negative values passed to this method disable connection validation. This check helps
detect connections that have become stale (half-closed) while kept inactive in the pool.

@since 4.4

@deprecated Use {@link #setConnectionConfigResolver(Resolver)}.
httpclient5/src/main/java/org/apache/hc/client5/http/impl/io/PoolingHttpClientConnectionManager.java