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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def allow( self, foreign, weight=None, permission="active", account=None, threshold=None, **kwargs ):
 """ Give additional access to an account by some other public key or account. :param str foreign: The foreign account that will obtain access :param int weight: (optional) The weight to use. If not define, the threshold will be used. If the weight is smaller than the threshold, additional signatures will be required. (defaults to threshold) :param str permission: (optional) The actual permission to modify (defaults to ``active``) :param str account: (optional) the account to allow access to (defaults to ``default_account``) :param int threshold: The threshold that needs to be reached by signatures to be able to interact """

        from copy import deepcopy

        if not account:
            if "default_account" in self.config:
                account = self.config["default_account"]
        if not account:
            raise ValueError("You need to provide an account")

        if permission not in ["owner", "active"]:
            raise ValueError("Permission needs to be either 'owner', or 'active")
        account = Account(account, blockchain_instance=self)

        if not weight:
            weight = account[permission]["weight_threshold"]

        authority = deepcopy(account[permission])
        try:
            pubkey = PublicKey(foreign, prefix=self.prefix)
            authority["key_auths"].append([str(pubkey), weight])
        except Exception:
            try:
                foreign_account = Account(foreign, blockchain_instance=self)
                authority["account_auths"].append([foreign_account["id"], weight])
            except Exception:
                raise ValueError("Unknown foreign account or invalid public key")
        if threshold:
            authority["weight_threshold"] = threshold
            self._test_weights_treshold(authority)

        op = operations.Account_update(
            **{
                "fee": {"amount": 0, "asset_id": "1.3.0"},
                "account": account["id"],
                permission: authority,
                "extensions": {},
                "prefix": self.prefix,
            }
        )
        if permission == "owner":
            return self.finalizeOp(op, account["name"], "owner", **kwargs)
        else:
            return self.finalizeOp(op, account["name"], "active", **kwargs)