'Give a nice string representation based on event ids.'

@property
def _name(self):

    if (len(self.event_id) == 1):
        comment = next(iter(self.event_id.keys()))
    else:
        count = np.bincount(self.events[:, 2])
        comments = list()
        for (key, value) in self.event_id.items():
            comments.append(('%.2f    *    %s' % ((float(count[value]) / len(self.events)), key)))
        comment = '    +    '.join(comments)
    return comment
