code: def merge_grad_list(all_grads, all_vars):
      """
      Args:
          all_grads (K x N): gradients
          all_vars(K x N): variables
  
      Return:
          K x N x 2: list of list of (grad, var) pairs
      """
      return [list(zip(gs, vs)) for gs, vs in zip(all_grads, all_vars)]
  
imports: import operator
  from contextlib import contextmanager
  import tensorflow
  import threading
  from ..compat import tfv1
  from ..tfutils.common import get_tf_version_tuple
  from ..tfutils.scope_utils import cached_name_scope, under_name_scope
  from ..tfutils.varreplace import custom_getter_scope
  from ..utils import logger
  from ..utils.argtools import call_only_once
label_desc: Use image node_id 5 for calling a global function with example usage: merge_grad_list(all_grads, all_vars) and returns: unknown