code: def get_input(self):
      input = Data(
          pos=self.xyz[self.iter],
          ind=self.ind[self.iter],
          size=self.ind_size[self.iter],
      )
      input_target = Data(
          pos=self.xyz_target[self.iter],
          ind=self.ind_target[self.iter],
          size=self.ind_size[self.iter],
      )
      return input, input_target
  
imports: import unittest
  import torch
  import numpy
  import os
  import random
  import sys
  from torch_geometric.data import Data
  from torch_points3d.utils.geometry import rodrigues
  from torch_points3d.metrics.registration_tracker import FragmentRegistrationTracker
label_desc: Use image node_id 3 for calling the MockModel obj's underlying member method code with example usage: obj.get_input() and returns: input,  input_target