def on_duplicate(self, ar, master):
        if self.ref:
            self.ref += '(DUP)'
        super(Referrable, self).on_duplicate(ar, master)
Constructs a FileKeyProvider based on the directory dir, and a
dataset/ETHPy150Open lsaffre/lino/lino/mixins/__init__.py/Referrable.on_duplicate--crossover with--dataset/ETHPy150Open spotify/crtauth/crtauth/ldap_key_provider.py/HybridKeyProvider.__init__