class_docstr: EventEmitter subclass used to allow deprecated events to be used with a
  warning message.
class_docstr_tok: ["EventEmitter","subclass","used","to","allow","deprecated","events","to","be","used","with","a","warning","message","."]
code: def _warn(self, cb):
      if self._warned:
          return
  
      # don't warn about unimplemented connections
      if isinstance(cb, tuple) and getattr(cb[0], cb[1], None) is None:
          return
  
      traceback.print_stack()
      logger.warning(self._message)
      self._warned = True
  
imports: from __future__ import division
  from collections import OrderedDict
  import inspect
  import traceback
  import weakref
  from .logs import logger, _handle_exception
label_desc: Use image node_id 4 for calling the WarningEmitter obj's underlying member method code with example usage: obj._warn(cb) without return types