public static BlockNumberProtocolSpec create(
        final long blockNumber, final ProtocolSpec protocolSpec) {
      return new BlockNumberProtocolSpec(blockNumber, protocolSpec);
    }
Associates a {@link ProtocolSpec} with a given block number or timestamp level starting point
Knows how to query the timestamp or block number of a given block header
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/mainnet/ScheduledProtocolSpec.java