How to use the bidict._common.KeyDuplicationError function in bidict

invbyval = inv.get(val, _MISS)
        isdupkey = fwdbykey is not _MISS
        isdupval = invbyval is not _MISS
        if isdupkey and isdupval:
            if self._isdupitem(key, val, invbyval, fwdbykey):
                # (key, val) duplicates an existing item -> no-op.
                return
            # key and val each duplicate a different existing item.
            if on_dup_kv is RAISE:
                raise KeyAndValueDuplicationError(key, val)
            elif on_dup_kv is IGNORE:
                return
            # else on_dup_kv is OVERWRITE. Fall through to return on last line.
        elif isdupkey:
            if on_dup_key is RAISE:
                raise KeyDuplicationError(key)
            elif on_dup_key is IGNORE:
                return
            # else on_dup_key is OVERWRITE. Fall through to return on last line.
        elif isdupval:
            if on_dup_val is RAISE:
                raise ValueDuplicationError(val)
            elif on_dup_val is IGNORE:
                return
            # else on_dup_val is OVERWRITE. Fall through to return on last line.
        # else neither isdupkey nor isdupval.
        return isdupkey, isdupval, invbyval, fwdbykey