code: def create_shortlink(self, callback_uri=None,
                           description=None, serial_number=None):
          
          arguments = {'callback_uri': callback_uri,
                       'description': description,
                       'serial_number': serial_number}
          return self.do_req('POST', self.merchant_api_base_url + '/shortlink/',
                             arguments).json()
docs: Register new shortlink
  
          Arguments:
              callback_uri:
                  URI called by mCASH when user scans shortlink
              description:
                  Shortlink description displayed in confirmation dialogs
              serial_number:
                  Serial number on printed QR codes. This field is only used when
                  registering printed stickers issued by mCASH