'Add labels.'

def __add__(self, other):

    if isinstance(other, Label):
        if (other.hemi == 'lh'):
            lh = (self.lh + other)
            rh = self.rh
        else:
            lh = self.lh
            rh = (self.rh + other)
    elif isinstance(other, BiHemiLabel):
        lh = (self.lh + other.lh)
        rh = (self.rh + other.rh)
    else:
        raise TypeError(('Need:    Label    or    BiHemiLabel.    Got:    %r' % other))
    name = ('%s    +    %s' % (self.name, other.name))
    color = _blend_colors(self.color, other.color)
    return BiHemiLabel(lh, rh, name, color)
