code: def reset_envs():
      """Reset common environment variable which are set in tests."""
      for key in [
          "DGL_ROLE",
          "DGL_NUM_SAMPLER",
          "DGL_NUM_SERVER",
          "DGL_DIST_MODE",
          "DGL_NUM_CLIENT",
          "DGL_DIST_MAX_TRY_TIMES",
          "DGL_DIST_DEBUG",
      ]:
          if key in os.environ:
              os.environ.pop(key)
  
file_path: dgl/tests/distributed/utils.py
imports: import os
  import random
  import socket
  import dgl
  import numpy
  import scipy.sparse
label_desc: Use image node_id 2 for calling a global function with example usage: reset_envs() without return types