code: def flag_calls(func):
      
  
      # don't wrap twice
      if hasattr(func, 'called'):
          return func
  
      def wrapper(*args, **kw):
          wrapper.called = False
          out = func(*args, **kw)
          wrapper.called = True
          return out
  
      wrapper.called = False
      wrapper.__doc__ = func.__doc__
      return wrapper
docs: Wrap a function to detect and flag when it gets called.
  
      This is a decorator which takes a function and wraps it in a function with
      a 'called' attribute. wrapper.called is initialized to False.
  
      The wrapper.called attribute is set to False right before each call to the
      wrapped function, so if the call fails it remains False.  After the call
      completes, wrapper.called is set to True and the output is returned.
  
      Testing for truth in wrapper.called allows you to determine if a call to
      func() was attempted and succeeded.