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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_frequency_shift( self, grid_points, temperatures=np.arange(0, 1001, 10, dtype='double'), epsilons=None, output_filename=None):
 """Frequency shift from lowest order diagram is calculated. Args: epslins(list of float):
 The value to avoid divergence. When multiple values are given frequency shifts for those values are returned. """


        if self._interaction is None:
            self.set_phph_interaction()
        if epsilons is None:
            _epsilons = [0.1]
        else:
            _epsilons = epsilons
        self._grid_points = grid_points
        get_frequency_shift(self._interaction,
                            self._grid_points,
                            self._band_indices,
                            _epsilons,
                            temperatures,
                            output_filename=output_filename,
                            log_level=self._log_level)