class_docstr: Concat gradients together to optimize transfer.
code: def __init__(self, num_split=8):
      self._num_split = num_split
  
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 1 to create a new GradientPacker object from inherited base classes: object with example: obj = GradientPacker(num_split)