@VisibleForTesting
  static BaseFeeMarket london(
      final long londonForkBlockNumber, final Optional<Wei> baseFeePerGasOverride) {
    return new LondonFeeMarket(londonForkBlockNumber, baseFeePerGasOverride);
  }
Creates a London fee market with the specified fork block number and optional base fee
override.

@param londonForkBlockNumber the block number at which the London fork activates.
@param baseFeePerGasOverride an optional override for the base fee per gas.
@return a {@link BaseFeeMarket} instance for the London fork.
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/mainnet/feemarket/FeeMarket.java