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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 _save_reference(self, filename):
 """ Performs an incomplete save of an existing SFrame into a directory. This saved SFrame may reference SFrames in other locations in the same filesystem for certain resources. Parameters filename : string The location to save the SFrame. Either a local directory or a remote URL. See Also -------- load_sframe, SFrame Examples -------- """

        ## Save the SFrame
        url = _make_internal_url(filename)

        with cython_context():
            self.__proxy__.save_reference(url)