code: def _l1_dist(edges):
      # formula 2
      ed = th.norm(edges.src["nd"] - edges.dst["nd"], 1, 1)
      return {"ed": ed}
  
imports: import dgl
  import dgl.function
  import numpy
  import torch
  import torch.nn
label_desc: Use image node_id 1 for calling a global function with example usage: _l1_dist(edges) and returns: dict