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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_apis(self):
 """Returns set of api names referenced in this Registry :return: set of api name strings """

        out = set(x.api for x in self.types.values() if x.api)
        for ft in self.features.values():
            out.update(ft.get_apis())
        for ext in self.extensions.values():
            out.update(ext.get_apis())
        return out