code: def iaf(self, model_configs, demo_data):
      model_configs.input_dim = tuple(demo_data["data"][0].shape)
      return IAF(model_configs)
  
imports: import os
  from copy import deepcopy
  import numpy
  import pytest
  import torch
  from pythae.data.datasets import BaseDataset
  from pythae.models import AutoModel
  from pythae.models.base.base_utils import ModelOutput
  from pythae.models.normalizing_flows import IAF, IAFConfig, NFModel
  from pythae.pipelines import TrainingPipeline
  from pythae.trainers import BaseTrainer, BaseTrainerConfig
label_desc: Use image node_id 2 for calling the Test_Model_forward obj's underlying member method code with example usage: obj.iaf(model_configs, demo_data) and returns: IAF