Verify a provided list of OTPs.

        :param max_time_window: Maximum number of seconds which can pass
                                between the first and last OTP generation for
                                the OTP to still be considered valid.
        :type max_time_window: ``int``

def verify_multi(self, otp_list, max_time_window=DEFAULT_MAX_TIME_WINDOW,
                     sl=None, timeout=None):
        """
        Verify a provided list of OTPs.

        :param max_time_window: Maximum number of seconds which can pass
                                between the first and last OTP generation for
                                the OTP to still be considered valid.
        :type max_time_window: ``int``
        """

        # Create the OTP objects
        otps = []
        for otp in otp_list:
            otps.append(OTP(otp, self.translate_otp))

        if len(otp_list) < 2:
            raise ValueError('otp_list needs to contain at least two OTPs')

        device_ids = set()
        for otp in otps:
            device_ids.add(otp.device_id)

        # Check that all the OTPs contain same device id
        if len(device_ids) != 1:
            raise Exception('OTPs contain different device ids')

        # Now we verify the OTPs and save the server response for each OTP.
        # We need the server response, to retrieve the timestamp.
        # It's possible to retrieve this value locally, without querying the
        # server but in this case, user would need to provide his AES key.
        for otp in otps:
            response = self.verify(otp.otp, True, sl, timeout,
                                   return_response=True)

            if not response:
                return False

            otp.timestamp = int(response['timestamp'])

        count = len(otps)
        delta = otps[count - 1].timestamp - otps[0].timestamp

        # OTPs have an 8Hz timestamp counter so we need to divide it to get
        # seconds
        delta = delta / 8

        if delta < 0:
            raise Exception('delta is smaller than zero. First OTP appears to '
                            'be older than the last one')

        if delta > max_time_window:
            raise Exception(('More than %s seconds have passed between '
                            'generating the first and the last OTP.') %
                            (max_time_window))

        return True