code: def select(target, src, edge, dst):
      if target == "u":
          return src
      elif target == "v":
          return dst
      elif target == "e":
          return edge
  
imports: import random
  import unittest
  import backend
  import dgl
  import numpy
  import pytest
  import torch
  from dgl.ops import gather_mm, gsddmm, gspmm, segment_reduce
  from utils import parametrize_idtype
  from utils.graph_cases import get_cases
label_desc: Use image node_id 1 for calling a global function with example usage: select(target, src, edge, dst) and returns: src, dst, edge