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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _check_unused_kwargs(self, kwargs):
 """ Call this at the end of call module to check if all the kwargs have been used. Assumes kwargs were extracted using pop. """

        if len(kwargs.keys()) != 0:
            unused = ""
            for k in kwargs.keys():
                unused += "'%s', "%k
            if unused[-2:] == ", ":     # get rid of trailing comma
                unused = unused[:-2]
            raise Exception('Unused keys in kwargs: %s'%unused)