code: def get_backbone(model: nn.Module):
      backbone = torch.nn.Sequential(*(list(model.children())[:-1]))
      return backbone
  
file_path: lightly/tests/models/test_ModelsSimSiam.py
imports: import unittest
  import torch
  import torch.nn
  import torchvision
  from lightly.models import SimSiam
label_desc: Use image node_id 2 for calling a global function with example usage: get_backbone(model) and returns: backbone