code: def check_pytorch():
      """Check if PyTorch is the backend."""
      if not HAS_TORCH:
          raise ModuleNotFoundError(
              "MovieLensDataset requires PyTorch to be the backend."
          )
  
imports: import os
  import numpy
  import pandas
  from torch import LongTensor, Tensor
  from ..base import dgl_warning
  from ..convert import heterograph
  from .dgl_dataset import DGLDataset
  from .utils import _get_dgl_url, download, extract_archive, load_graphs, load_info, save_graphs, save_info, split_dataset
label_desc: Use image node_id 1 for calling a global function with example usage: check_pytorch() without return types