public List<RequestSpec<K>> poll() {
        List<RequestSpec<K>> requests = new ArrayList<>();
        collectLookupRequests(requests);
        collectFulfillmentRequests(requests);
        return requests;
    }
Check whether any requests need to be sent. This should be called immediately
after the driver is constructed and then again after each request returns
(i.e. after {@link #onFailure(long, RequestSpec, Throwable)} or
{@link #onResponse(long, RequestSpec, AbstractResponse, Node)}).

@return A list of requests that need to be sent
clients/src/main/java/org/apache/kafka/clients/admin/internals/AdminApiDriver.java