@VisibleForTesting
  public static Collection<EnodeURL> getFixedNodes(
      final Collection<EnodeURL> someFixedNodes, final Collection<EnodeURL> moreFixedNodes) {
    final Collection<EnodeURL> fixedNodes = new ArrayList<>(someFixedNodes);
    fixedNodes.addAll(moreFixedNodes);
    return fixedNodes;
  }
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