docstr: Inverse function to size2class 
docstr_tok: ["Inverse","function","to","size2class"]
code: def class2size(self, pred_cls, residual):
      """Inverse function to size2class"""
      if torch.is_tensor(residual):
          mean = torch.tensor(self.mean_size_arr[pred_cls, :]).to(
              residual.device
          )
      else:
          mean = self.mean_size_arr[pred_cls, :]
      return mean + residual
  
imports: import os
  import numpy
  import torch
  import logging
  from torch_geometric.data import InMemoryDataset
  from torch_points3d.datasets.segmentation.scannet import Scannet, NUM_CLASSES, IGNORE_LABEL
  from torch_points3d.metrics.object_detection_tracker import ObjectDetectionTracker
  from torch_points3d.datasets.base_dataset import BaseDataset, save_used_properties
  from torch_points3d.utils.box_utils import box_corners_from_param
label_desc: Use image node_id 5 for calling the ScannetDataset obj's underlying member method code with example usage: obj.class2size(pred_cls, residual) and returns: unknown