def METHOD_NAME(self, num_tx):
    threads = []
    def ensure_generate_block(node, txs):
        block_hash = RpcClient(node).METHOD_NAME(txs)
        assert_is_hash_string(block_hash)
    for idx in self.sample_node_indices():
        t = threading.Thread(target=ensure_generate_block, args=(self.nodes[idx], num_tx), daemon=True)
        threads.append(t)
        t.start()
    for t in threads:
        t.join()