<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_backdoor(self, backdoor_name, source, reference, method='', aliases=[], version='', campaign='', confidence='', description='', bucket_list=[]):
 """ Add a backdoor object to CRITs. Args: backdoor_name: The primary name of the backdoor source: Source of the information reference: A reference where more information can be found method: The method for obtaining the backdoor information. aliases: List of aliases for the backdoor. version: Version campaign: An associated campaign confidence: The campaign confidence description: A description of the email bucket_list: A list of bucket list items to add """

        data = {
            'api_key': self.api_key,
            'username': self.username,
            'source': source,
            'reference': reference,
            'method': method,
            'name': backdoor_name,
            'aliases': ','.join(aliases),
            'version': version,
            'campaign': campaign,
            'confidence': confidence,
            'bucket_list': bucket_list,
            'description': description,
        }
        r = requests.post('{0}/backdoors/'.format(self.url),
                          data=data,
                          verify=self.verify,
                          proxies=self.proxies)
        if r.status_code == 200:
            result_data = json.loads(r.text)
            return result_data
        else:
            log.error('Error with status code {0} and message '
                      '{1}'.format(r.status_code, r.text))
        return None