Validate client's PIN.  Uses PUT to /clients/<client> interface.

        :Args:
            * *client*: (str) Client's ID
            * *pin*: (str) Client's PIN

def client_validate_pin(self, client, pin):
        """
        Validate client's PIN.  Uses PUT to /clients/<client> interface.

        :Args:
            * *client*: (str) Client's ID
            * *pin*: (str) Client's PIN
        """

        client = self._client_id(client)
        body = {
            "action": "validate_pin",
            "current_pin": pin
        }

        response = self._put(url.clients_id.format(id=client), body=body)
        self._check_response(response, 200)