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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 app(self):
 """Internal method that will supply the app to use internally. Returns: flask.Flask: The app to use within the component. Raises: RuntimeError: This is raised if no app was provided to the component and the method is being called outside of an application context. """

        app = self._app or current_app

        if not in_app_context(app):
            raise RuntimeError("This component hasn't been initialized yet "
                               "and an app context doesn't exist.")

        # If current_app is the app, this must be used in order for their IDs
        # to be the same, as current_app will wrap the app in a proxy.
        if hasattr(app, '_get_current_object'):
            app = app._get_current_object()

        return app