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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 set_dtreat_dfit(self, dfit=None):
 """ Set the fitting dictionnary A dict contaning all parameters for fitting the data Valid dict content includes: - 'type': str 'fft': A fourier filtering 'svd': A svd filtering """

        warnings.warn("Not implemented yet !, dfit forced to None")
        dfit = None

        assert dfit is None or isinstance(dfit,dict)
        if isinstance(dfit,dict):
            assert 'type' in dfit.keys()
            assert dfit['type'] in ['svd','fft']

        self._dtreat['dfit'] = dfit
        self._ddata['uptodate'] = False