private BlockHeader getHeaderForCurrentChainHead() {
    return blockchain.getBlockHeader(blockchain.getChainHeadHash()).get();
  }
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/frontier/EthGetFilterChangesIntegrationTest.java