code: def is_undirected(
      edge_index: Tensor,
      edge_attr: Optional[Tensor] = None,
      num_nodes: Optional[int] = None,
  ) -> bool:
      pass
  
file_path: pytorch_geometric/torch_geometric/utils/undirected.py
imports: import typing
  from typing import List, Optional, Tuple, Union
  import torch
  from torch import Tensor
  from torch_geometric.typing import OptTensor
  from torch_geometric.utils import coalesce, sort_edge_index
  from torch_geometric.utils.num_nodes import maybe_num_nodes
label_desc: Use image node_id 1 for calling a global function with example usage: is_undirected(edge_index, edge_attr, num_nodes) without return types