code: def get_dataset(dataset_root, dataset_name):
      if dataset_name.lower() in list(MoleculeDataset.names.keys()):
          return MoleculeDataset(root=dataset_root, name=dataset_name)
      elif dataset_name.lower() in [
          "graph_sst2",
          "graph_sst5",
          "twitter",
      ]:
          return SentiGraphDataset(root=dataset_root, name=dataset_name)
      elif dataset_name.lower() in list(SynGraphDataset.names.keys()):
          return SynGraphDataset(root=dataset_root, name=dataset_name)
      elif dataset_name.lower() in ["ba_lrp"]:
          return BA_LRP(root=dataset_root)
      else:
          raise ValueError(f"{dataset_name} is not defined.")
  
imports: import torch
  from torch.utils.data import random_split, Subset
  from torch_geometric.data import DataLoader
  from dig.xgraph.dataset import MoleculeDataset, SynGraphDataset, SentiGraphDataset, BA_LRP
  from torch import default_generator
label_desc: Use image node_id 1 for calling a global function with example usage: get_dataset(dataset_root, dataset_name) and returns: MoleculeDataset, SentiGraphDataset, SynGraphDataset, BA_LRP