code: def _build_network(self):
      if self.hparams.grouped_features:
          # converting the grouped_features into a nested list of indices
          features = (
              self.hparams.categorical_cols
              + self.hparams.continuous_cols
          )
          grp_list = [
              [features.index(col) for col in grp if col in features]
              for grp in self.hparams.grouped_features
          ]
      else:
          # creating a default grp_list with each feature as a group
          grp_list = [
              [i]
              for i in range(
                  self.hparams.continuous_dim
                  + self.hparams.categorical_dim
              )
          ]
      group_matrix = create_group_matrix(
          grp_list,
          self.hparams.continuous_dim + self.hparams.categorical_dim,
      )
      self.tabnet = TabNet(
          input_dim=self.hparams.continuous_dim
          + self.hparams.categorical_dim,
          output_dim=self.hparams.output_dim,
          n_d=self.hparams.n_d,
          n_a=self.hparams.n_a,
          n_steps=self.hparams.n_steps,
          gamma=self.hparams.gamma,
          cat_idxs=list(range(self.hparams.categorical_dim)),
          cat_dims=[
              cardinality
              for cardinality, _ in self.hparams.embedding_dims
          ],
          cat_emb_dim=[
              embed_dim for _, embed_dim in self.hparams.embedding_dims
          ],
          n_independent=self.hparams.n_independent,
          n_shared=self.hparams.n_shared,
          epsilon=1e-15,
          virtual_batch_size=self.hparams.virtual_batch_size,
          momentum=0.02,
          mask_type=self.hparams.mask_type,
          group_attention_matrix=group_matrix,
      )
  
imports: from typing import Dict
  import torch
  import torch.nn
  from omegaconf import DictConfig
  from pytorch_tabnet.tab_network import TabNet
  from pytorch_tabnet.utils import create_group_matrix
  from ..base_model import BaseModel
label_desc: Use image node_id 2 for calling the TabNetBackbone obj's underlying member method code with example usage: obj._build_network() without return types