message: Add comment for getVoxelPtrByGlobalIndex(...) method.
diff: @@ -165,6 +165,8 @@ class Layer {
  return block_map_.count(block_index) > 0;
  }
  + // Get a pointer to the voxel if its corresponding block is allocated and a
  + // nullptr otherwise.
  inline VoxelType* getVoxelPtrByGlobalIndex(
  const VoxelIndex& global_voxel_index) {
  const BlockIndex block_index = getBlockIndexFromGlobalVoxelIndex(
  