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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 clear(self, pat=None):
 """ Minor diversion with built-in dict here; clear can take a glob style expression and remove keys based on that expression. """

        if pat is None:
            return self.__dict__.clear()

        expr = re.compile(fnmatch.translate(pat))
        for key in tuple(self.keys()):
            #make sure the key is a str first
            if isinstance(key, string_types):
                if expr.match(key):
                    del self.__dict__[key]