class_docstr: A callback which proxy all methods to another callback.
  It's useful as a base class of callbacks which decorate other callbacks.
class_docstr_tok: ["A","callback","which","proxy","all","methods","to","another","callback",".","It","'s","useful","as","a","base","class","of","callbacks","which","decorate","other","callbacks","."]
docstr: Args:
      cb(Callback): the underlying callback
code: def __init__(self, cb):
      """
      Args:
          cb(Callback): the underlying callback
      """
      assert isinstance(cb, Callback), type(cb)
      self.chief_only = cb.chief_only
      self.cb = cb
  
imports: from abc import ABCMeta
  import six
  from ..compat import tfv1
  from ..tfutils.common import get_op_or_tensor_by_name
label_desc: Use image node_id 1 to create a new ProxyCallback object from inherited base classes: Callback with example: obj = ProxyCallback(cb)