class_docstr: Helper for @contextmanager decorator.
class_docstr_tok: ["Helper","for","@","contextmanager","decorator","."]
code: def __enter__(self):
      try:
          return next(self.gen)
      except StopIteration:
          raise RuntimeError("generator didn't yield")
  
imports: import abc
  import sys
  import warnings
  from collections import deque
  from functools import wraps
label_desc: Use image node_id 3 for calling the _GeneratorContextManager obj's underlying member method code with example usage: obj.__enter__() and returns: next