code: def forward(self, x: torch.Tensor, t1=None, t2=None, t3=None):
      return {"x": x, "t1": t1, "t2": t2, "t3": t3}
  
file_path: MONAI/tests/test_prepare_batch_extra_input.py
imports: from __future__ import annotations
  import unittest
  import torch
  from parameterized import parameterized
  from monai.engines import PrepareBatchExtraInput, SupervisedEvaluator
  from tests.utils import assert_allclose
label_desc: Use image node_id 1 for calling the TestNet obj's underlying member method code with example usage: obj.forward(x, t1, t2, t3) and returns: dict