code: def subgraph_collate_fn(g, batch):
      nids = np.concatenate(batch).reshape(-1).astype(np.int64)
      g1 = g.subgraph(nids)
      g1 = dgl.remove_self_loop(g1)
      g1 = dgl.add_self_loop(g1)
      return g1
  
file_path: dgl/examples/pytorch/ogb/cluster-gat/sampler.py
imports: import os
  import torch
  from partition_utils import *
label_desc: Use image node_id 1 for calling a global function with example usage: subgraph_collate_fn(g, batch) and returns: g1