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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 send_sms(phone: str, message: str, sender: str='', **kw):
 """ Sends SMS via Kajala Group SMS API. Contact info@kajala.com for access. :param phone: Phone number :param message: Message to be esnd :param sender: Sender (max 11 characters) :param kw: Variable key-value pairs to be sent to SMS API :return: Response from requests.post """

    if not hasattr(settings, 'SMS_TOKEN'):
        raise Exception('Invalid configuration: settings.SMS_TOKEN missing')
    if not sender:
        sender = settings.SMS_SENDER_NAME
    if not sender:
        raise Exception('Invalid configuration: settings.SMS_SENDER_NAME missing')
    headers = {
        'Content-Type': 'application/json',
        'Authorization': 'Token ' + settings.SMS_TOKEN,
    }
    data = {
        'dst': phone_filter(phone),
        'msg': message,
        'src': sender,
    }
    for k, v in kw.items():
        data[k] = v
    return requests.post("https://sms.kajala.com/api/sms/", json=data, headers=headers)