[SupervoxelClustering] setIndices not working on SupervoxelClustering Classs

Describe the bug
When using the superVoxelClustering class to segment objects in a scene using LCCP, I'd like to do so only on a subset of the points, (ie, removing the indices that correspond to the plane, and/or those too far away from the camera). I obtain these desired indices to be considered and pass them to the class using the setIndices function, but the supervoxels get computed for the totality of the input pointcloud, and therefore also the LCCP segmentation. I need the output to be in form of indices from the original pointcloud.

Context
My goal is to perform LCCP segmentation on a subset of indices of the original pointcloud.

Expected behavior
Like most other PCL functions, superVoxelClustering inherits setIndices from PCLBase. However, it seems to ignore this indices, since the result is computed on the whole input pointcloud

Current Behavior
Instead of computing the superVoxelClustering using the subset of indices passed via setIndices, it computes it for all the pointcloud.

To Reproduce
Same code as the lccp example,
https://github.com/PointCloudLibrary/pcl/blob/master/examples/segmentation/example_lccp_segmentation.cpp
where lines 272 to 319 have been modified as follows, to make use of indices:

(input pointcloud is any pointcloud with a plane and some objects on top of it. )

// Find plane  in pointcloud
pcl::PointIndices::Ptr plane_ids(new pcl::PointIndices);
pcl::ModelCoefficients::Ptr coeffs(new pcl::ModelCoefficients);
pcl::SACSegmentation<pcl::PointXYZRGBNormal> seg;
seg.setOptimizeCoefficients(true);
seg.setMaxIterations(200);
seg.setModelType(pcl::SACMODEL_PLANE);
seg.setMethodType(pcl::SAC_RANSAC);
seg.setDistanceThreshold(0.01);
seg.setInputCloud(input_pointcloud);
seg.segment(*plane_ids, *coeffs);

// Extract indices of points not in plane
pcl::PointIndices::Ptr non_plane_ids(new pcl::PointIndices);
pcl::PointCloud<pcl::PointXYZRGBNormal>::Ptr non_plane_cloud(new pcl::PointCloud<pcl::PointXYZRGBNormal>);
pcl::ExtractIndices<pcl::PointXYZRGBNormal> extract;
extract.setInputCloud(input_pointcloud);
extract.setIndices(plane_ids);
extract.setNegative(true);
extract.filter(non_plane_ids->indices);
extract.filter(*non_cloud_plane);

// Split pointcloud to fit SuperVoxelClustering input format
pcl::PointCloud<PointT>::Ptr cloud_RGB(new pcl::PointCloud<PointT>);
pcl::PointCloud<pcl::Normal>::Ptr cloud_normals(new pcl::PointCloud<pcl::Normal>);
pcl::copyPointCloud(*input_pointcloud, *cloud_RGB);
pcl::copyPointCloud(*input_pointcloud, *cloud_normals);

// Compute SuperVoxel Clustering
pcl::SupervoxelClustering<PointT> super(0.005, 0.02);
super.setUseSingleCameraTransform(false);
super.setInputCloud(cloud_RGB);
super.setNormalCloud(cloud_normals);
super.setIndices(non_plane_ids);         // <------------------- XXXX This is the line where the bug is XXXXX
super.setColorImportance(0.0f);
super.setSpatialImportance(1.0f);
super.setNormalImportance(4.0f);
std::map<std::uint32_t, pcl::Supervoxel<PointT>::Ptr> supervoxel_clusters;
PCL_INFO("Extracting supervoxels\n");
super.extract(supervoxel_clusters);
super.refineSupervoxels(2, supervoxel_clusters);

PCL_INFO("Getting supervoxel adjacency\n");
std::multimap<std::uint32_t, std::uint32_t> supervoxel_adjacency;
super.getSupervoxelAdjacency(supervoxel_adjacency);

PCL_INFO("Starting LCCP Segmentation\n");
pcl::LCCPSegmentation<PointT> lccp;
lccp.setConcavityToleranceThreshold(10.0);
lccp.setSanityCheck(false);
lccp.setSmoothnessCheck(true, 0.005, 0.02, 0.1);
lccp.setKFactor(1);
lccp.setInputSupervoxels(supervoxel_clusters, supervoxel_adjacency);
lccp.setMinSegmentSize(5);
lccp.segment();

PCL_INFO("Interpolation voxel cloud -> input cloud and relabeling\n");
pcl::PointCloud<pcl::PointXYZL>::Ptr sv_labeled_cloud = super.getLabeledCloud();
pcl::PointCloud<pcl::PointXYZL>::Ptr lccp_labeled_cloud = sv_labeled_cloud->makeShared();
lccp.relabelCloud(*lccp_labeled_cloud);
SuperVoxelAdjacencyList sv_adjacency_list;
lccp.getSVAdjacencyList (sv_adjacency_list);  // Needed for visualization

Screenshots/Code snippets
Example (but repeats in every example):
Original Pointcloud (input_pointcloud):

Pointcloud after plane removal (non_plane_cloud)

Supervoxel clustering results (despite setIndices(non_plane_ids):

LCCP Segmentation results:

Your Environment (please complete the following information):

• OS: Ubuntu 18.04
• Compiler:GCC 7.5
• PCL Version 1.8

Possible Solution

Not obligatory, but suggest a fix/reason for the bug. Feel free to create a PR if you feel comfortable.

Additional context

Add any other context about the problem here.

Start with examples/segmentation/example_lccp_segmentation.cpp and trace SupervoxelClustering::setIndices through extract(), using the issue's modified code to reproduce the behavior. Done means clustering and subsequent LCCP segmentation use only the supplied subset while preserving indices from the original point cloud.