class_docstr: Context manager to capture and suppress expected log output.
  
  Useful to make tests of error conditions less noisy, while still
  leaving unexpected log entries visible.  *Not thread safe.*
  
  The attribute ``logged_stack`` is set to true if any exception
  stack trace was logged.
  
  Usage::
  
      with ExpectLog('tornado.application', "Uncaught exception"):
          error_response = self.fetch("/some_page")
  
  .. versionchanged:: 4.3
     Added the ``logged_stack`` attribute.
code: def __exit__(self, typ, value, tb):
      self.logger.removeFilter(self)
      if not typ and self.required and not self.matched:
          raise Exception("did not get expected log message")
  
imports: from __future__ import absolute_import, division, print_function
  from tornado.log import gen_log, app_log
  from tornado.stack_context import ExceptionStackContext
  from tornado.util import raise_exc_info, basestring_type, PY3
  import functools
  import inspect
  import logging
  import os
  import re
  import signal
  import socket
  import sys
label_desc: Use image node_id 4 for calling the ExpectLog obj's underlying member method code with example usage: obj.__exit__(typ, value, tb) without return types