class_docstr: Single global state to keep track of scope stacks.
code: def global_scope(self):
      return NameScope()
  
imports: from collections import defaultdict
  from collections.abc import Iterable
  from functools import singledispatch
  import pyro
  from pyro.poutine.handlers import _make_handler
  from pyro.poutine.reentrant_messenger import ReentrantMessenger
  from pyro.poutine.runtime import effectful
label_desc: Use image node_id 3 for calling the ScopeStack obj's underlying member method code with example usage: obj.global_scope() and returns: NameScope