static BaseFeeMarket zeroBaseFee(final long londonForkBlockNumber) {
    return new ZeroBaseFeeMarket(londonForkBlockNumber);
  }
Creates a fee market with a zero base fee.

@param londonForkBlockNumber the block number at which the London fork activates.
@return a {@link BaseFeeMarket} instance with a zero base fee.
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/mainnet/feemarket/FeeMarket.java