Waits until the chain has a block above "after_block" (default: the current head) and returns it: number, hash, parent hash, timestamp, miner, difficulty, gas used, transaction count and subsidy, with a reorg marker if the tip was replaced instead. Blocks come every 10 minutes on average, but intervals vary widely, so a wait can time out: then it returns "new_block": false with the current head, and you can call it again. "timeout_seconds" defaults to 120, at most 600 (90 on servers running without HTTP sessions). For clients that support resource subscriptions, subscribing to parallax://chain/head is the better way to follow the chain. Use this to wait for a transaction's next confirmation, then check it with get_receipt.