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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 get_subregions(self, iso_code):
 """ Returns subregion calendar classes for given region iso_code. {'DE-HH': <class 'workalendar.europe.germany.Hamburg'>, 'DE-BE': <class 'workalendar.europe.germany.Berlin'>} :rtype dict :return dict where keys are ISO codes strings and values are calendar classes """

        items = OrderedDict()
        for key, value in self.region_registry.items():
            code_elements, is_subregion = self._code_elements(key)
            if is_subregion and code_elements[0] == iso_code:
                items[key] = value
        return items