Implement label hacks: Hide trailing @, remove label with leading @

        Labels split with $\mid$ symbol will be treated for each part.

def _sanitise_label_group(cls, labelgroup):
        """Implement label hacks: Hide trailing @, remove label with leading @

        Labels split with $\mid$ symbol will be treated for each part.
        """

        if r'$\mid$' in labelgroup:
            label_components = labelgroup.split(r'$\mid$')
            good_labels = [l for l in
                           map(cls._sanitise_label, label_components)
                           if l is not None]
            if len(good_labels) == 0:
                return None
            else:
                return r'$\mid$'.join(good_labels)
        else:
            return cls._sanitise_label(labelgroup)