private Optional<MetricsService> createMetricsService(final MetricsConfiguration configuration) {
    return MetricsService.create(configuration, metricsSystem);
  }
Gets fixed nodes. Visible for testing.

@param someFixedNodes the fixed nodes
@param moreFixedNodes nodes added to fixed nodes
@return the fixed and more nodes combined
app/src/main/java/org/hyperledger/besu/RunnerBuilder.java