Remove frequencies from the dataset

def remove_frequencies(self, fmin, fmax):
        """Remove frequencies from the dataset
        """
        self.data.query(
            'frequency > {0} and frequency < {1}'.format(fmin, fmax),
            inplace=True
        )
        g = self.data.groupby('frequency')
        print('Remaining frequencies:')
        print(sorted(g.groups.keys()))