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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 fitted_parameters(self):
 """ A tuple of fitted values for the `scipy_data_fitting.Fit.fitting_parameters`. The values in this tuple are not scaled by the prefix, as they are passed back to `scipy_data_fitting.Fit.function`, e.g. in most standard use cases these would be the SI values. If no fitting parameters were specified, this will just return an empty tuple. """

        if hasattr(self,'_fitted_parameters'): return self._fitted_parameters
        if not self.fitting_parameters: return tuple()
        if self.options['fit_function'] == 'lmfit':
            return tuple( self.curve_fit.params[key].value for key in sorted(self.curve_fit.params) )
        else:
            return tuple(self.curve_fit[0])