code: def cancel_letter(self, pixelletter_id):
          
          cancel_request = self._make_delete_request('letters/{}'.format(pixelletter_id))
          status = json.loads(cancel_request)['status']
  
          if status == 200:
              return True
  
          return False
docs: Cancel specified letter
          :param pixelletter_id: ID of the letter
          :return: True if canceled, else False