Derive deterministic keypair from **seed** based on **index**

        :param seed: Seed used to get keypair
        :type seed: str

        :param index: Index of the generated keypair
        :type index: int

        :raises: :py:exc:`nano.rpc.RPCException`

        >>> rpc.deterministic_key(
        ...     seed="0000000000000000000000000000000000000000000000000000000000000000",
        ...     index=0
        ... )
        {
          "private": "9F0E444C69F77A49BD0BE89DB92C38FE713E0963165CCA12FAF5712D7657120F",
          "public": "C008B814A7D269A1FA3C6528B19201A24D797912DB9996FF02A1FF356E45552B",
          "account": "xrb_3i1aq1cchnmbn9x5rsbap8b15akfh7wj7pwskuzi7ahz8oq6cobd99d4r3b7"
        }

def deterministic_key(self, seed, index):
        """
        Derive deterministic keypair from **seed** based on **index**

        :param seed: Seed used to get keypair
        :type seed: str

        :param index: Index of the generated keypair
        :type index: int

        :raises: :py:exc:`nano.rpc.RPCException`

        >>> rpc.deterministic_key(
        ...     seed="0000000000000000000000000000000000000000000000000000000000000000",
        ...     index=0
        ... )
        {
          "private": "9F0E444C69F77A49BD0BE89DB92C38FE713E0963165CCA12FAF5712D7657120F",
          "public": "C008B814A7D269A1FA3C6528B19201A24D797912DB9996FF02A1FF356E45552B",
          "account": "xrb_3i1aq1cchnmbn9x5rsbap8b15akfh7wj7pwskuzi7ahz8oq6cobd99d4r3b7"
        }

        """

        seed = self._process_value(seed, 'seed')
        index = self._process_value(index, 'int')

        payload = {"seed": seed, "index": index}

        resp = self.call('deterministic_key', payload)

        return resp