private Block appendBlock(
      final Difficulty difficulty,
      final BlockHeader parentBlock,
      final Transaction... transactionsToAdd) {
    final List<Transaction> transactionList = asList(transactionsToAdd);
    final Block block =
        new Block(
            new BlockHeaderTestFixture()
                .difficulty(difficulty)
                .parentHash(parentBlock.getHash())
                .number(parentBlock.getNumber() + 1)
                .buildHeader(),
            new BlockBody(transactionList, emptyList()));
    final List<TransactionReceipt> transactionReceipts =
        transactionList.stream()
            .map(transaction -> new TransactionReceipt(1, 1, emptyList(), Optional.empty()))
            .collect(toList());
    blockchain.appendBlock(block, transactionReceipts);
    return block;
  }
Determines whether a specified filter exists.

@param filterId The filter ID to check.
@return A boolean - true if the filter exists, false if not.
ethereum/api/src/integration-test/java/org/hyperledger/besu/ethereum/api/jsonrpc/methods/fork/london/EthGetFilterChangesIntegrationTest.java