Returns the list of kpoint indices equivalent (meaning they are the
        same frac coords) to the given one.

        Args:
            index: the kpoint index

        Returns:
            a list of equivalent indices

        TODO: now it uses the label we might want to use coordinates instead
        (in case there was a mislabel)

def get_equivalent_kpoints(self, index):
        """
        Returns the list of kpoint indices equivalent (meaning they are the
        same frac coords) to the given one.

        Args:
            index: the kpoint index

        Returns:
            a list of equivalent indices

        TODO: now it uses the label we might want to use coordinates instead
        (in case there was a mislabel)
        """
        # if the kpoint has no label it can"t have a repetition along the band
        # structure line object

        if self.kpoints[index].label is None:
            return [index]

        list_index_kpoints = []
        for i in range(len(self.kpoints)):
            if self.kpoints[i].label == self.kpoints[index].label:
                list_index_kpoints.append(i)

        return list_index_kpoints