private Optional<BlockHeader> determineBlockHeader(final JsonRpcRequestContext request) {
    final Hash hash;
    try {
      hash = request.getRequiredParameter(0, Hash.class);
    } catch (JsonRpcParameterException e) {
      throw new InvalidJsonRpcParameters(
          "Invalid block hash parameter (index 0)", RpcErrorType.INVALID_BLOCK_HASH_PARAMS, e);
    }
    return blockchainQueries.blockByHash(hash).map(BlockWithMetadata::getHeader);
  }
Instantiates a new Clique get signers at hash.

@param blockchainQueries the blockchain queries
@param validatorProvider the validator provider
consensus/clique/src/main/java/org/hyperledger/besu/consensus/clique/jsonrpc/methods/CliqueGetSignersAtHash.java