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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_features(self, api=None):
 """Returns filtered list of features in this registry :param str api: Return only features with this api name, or None to return all features. :return: list of Feature objects """

        return [x for x in self.features.values()
                if api and x.api == api or not api]