public static PoWHasher powHasher(final PowAlgorithm powAlgorithm) {
    if (powAlgorithm == null) {
      return PoWHasher.UNSUPPORTED;
    }
    return powAlgorithm == PowAlgorithm.ETHASH ? PoWHasher.ETHASH_LIGHT : PoWHasher.UNSUPPORTED;
  }
Provides the various {@link ProtocolSpec}s on mainnet hard forks.
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/mainnet/MainnetProtocolSpecs.java