code: def wait(value, must_be_child=False):
      '''Wait for a possible asynchronous value to complete.
      '''
      current = getcurrent()
      parent = current.parent
      if must_be_child and not parent:
          raise MustBeInChildGreenlet('Cannot wait on main greenlet')
      return parent.switch(value) if parent else valuf wait(value, must_be_child=False):
      '''Wait for a possible asynchronous value to complete.
      '''
      current = getcurrent()
      parent = current.parent
      if must_be_child and not parent:
          raise MustBeInChildGreenlet('Cannot wait on main greenlet')
      return parent.switch(value) if parent else value
docs: Wait for a possible asynchronous value to complete.