private boolean isCheckpointPoSBlock(final GenesisConfigOptions configOptions) {
      final UInt256 terminalTotalDifficulty = configOptions.getTerminalTotalDifficulty().get();

      return configOptions.getCheckpointOptions().isValid()
          && (UInt256.fromHexString(configOptions.getCheckpointOptions().getTotalDifficulty().get())
              .greaterThan(terminalTotalDifficulty));
    }
From genesis config besu controller builder.

@param genesisConfig the genesis config file
@param syncMode the sync mode
@return the besu controller builder
app/src/main/java/org/hyperledger/besu/controller/BesuController.java