def __repr__(self):
        cid = str(self.identifier)
        if self.parent:
            pid = str(self.parent.identifier)
        else:
            pid = '-'
        if self.childs:
            ch = ','.join(['{}'.format(c.identifier) for c in self.childs])
        else:
            ch = '-'
        return cid+';p:'+pid+';ch:'+ch