class_docstr: Resets the `StackContext`.
  
  Useful when creating a shared resource on demand (e.g. an
  `.AsyncHTTPClient`) where the stack that caused the creating is
  not relevant to future operations.
class_docstr_tok: ["Resets","the","`","StackContext","`",".","Useful","when","creating","a","shared","resource","on","demand","(","e.g",".","an","`",".AsyncHTTPClient","`",")","where","the","stack","that","caused","the","creating","is","not","relevant","to","future","operations","."]
code: def __exit__(self, type, value, traceback):
      _state.contexts = self.old_contexts
  
imports: from __future__ import absolute_import, division, print_function
  import sys
  import threading
  from tornado.util import raise_exc_info
label_desc: Use image node_id 2 for calling the NullContext obj's underlying member method code with example usage: obj.__exit__(type, value, traceback) without return types