code: def _read_all(dl: DataLoader):
      return torch.cat([x for x, in dl], dim=0)
  
imports: import unittest
  from typing import Optional
  import torch
  import torch.nn
  from opacus import PrivacyEngine
  from opacus.data_loader import DPDataLoader, switch_generator
  from opacus.grad_sample import GradSampleModule
  from opacus.optimizers import DPOptimizer
  from torch.utils.data import DataLoader, TensorDataset
label_desc: Use image node_id 2 for calling a global function with example usage: _read_all(dl) and returns: torch