def whois(cls, whois_server, domain=None, timeout=None):  # pragma: no cover
        """
        Implementation of UNIX whois.

        :param whois_server: The WHOIS server to use to get the record.
        :type whois_server: str

        :param domain: The domain to get the whois record from.
        :type domain: str

        :param timeout: The timeout to apply to the request.
        :type timeout: int

        :return: The whois record from the given whois server, if exist.
        :rtype: str|None
        """

        if domain is None:
            # The domain is not given (localy).

            # We consider the domain as the domain or IP we are currently testing.
            domain = PyFunceble.INTERN["to_test"]

        if timeout is None:
            # The time is not given (localy).

            # We consider the timeout from the configuration as the timeout to use.
            timeout = PyFunceble.CONFIGURATION["seconds_before_http_timeout"]

        if whois_server:
            # A whois server is given.

            # We initiate a PyFunceble.socket.
            req = PyFunceble.socket.socket(
                PyFunceble.socket.AF_INET, PyFunceble.socket.SOCK_STREAM
            )

            if timeout % 3 == 0:
                # The timeout is modulo 3.

                # We report the timeout to our initiated PyFunceble.socket.
                req.settimeout(timeout)
            else:
                # The timeout is not modulo 3.

                # We report 3 seconds as the timeout to our initiated PyFunceble.socket.
                req.settimeout(3)

            try:
                # We try to connect to the whois server at the port 43.
                req.connect((whois_server, 43))
            except PyFunceble.socket.error:
                # We got an error.

                # We return None.
                return None

            # We send end encode the domain we want the data from.
            req.send((domain + "\r\n").encode())

            # We initiate a bytes variable which will save the response
            # from the server.
            response = b""

            while True:
                # We loop infinitly.
                try:
                    # We try to receive the data in a buffer of 4096 bytes.
                    data = req.recv(4096)
                except (PyFunceble.socket.timeout, ConnectionResetError):
                    # We got an error.

                    # We close the connection.
                    req.close()

                    # And we return None.
                    return None

                # Everything goes right.

                # We append data to the response we got.
                response += data

                if not data:
                    # The data is empty.

                    # We break the loop.
                    break

            # We close the connection.
            req.close()

            try:

                # We finally decode and return the response we got from the
                # server.
                return response.decode()

            except UnicodeDecodeError:
                # We got an encoding error.

                # We decode the response.
                # Note: Because we don't want to deal with other issue, we
                # decided to use `replace` in order to automatically replace
                # all non utf-8 encoded characters.
                return response.decode("utf-8", "replace")

        # The whois server is not given.

        # We return None.
        return None
Implementation of UNIX whois.

        :param whois_server: The WHOIS server to use to get the record.
        :type whois_server: str

        :param domain: The domain to get the whois record from.
        :type domain: str

        :param timeout: The timeout to apply to the request.
        :type timeout: int

        :return: The whois record from the given whois server, if exist.
        :rtype: str|None