code: def add_event(self, user_id, event_name, event_properties=None, headers=None, endpoint_url=None):
          
          endpoint_url = endpoint_url or self._endpoint_url
  
          url = endpoint_url + '/users/' + user_id + '/events'
          headers = headers or self._default_headers()
  
          event_properties = event_properties or {}
          payload = {
              "event_name": event_name,
              "custom_properties": event_properties
          }
  
          response = requests.post(url, headers=headers, json=payload)
  
          return response
docs: Send an identified event. If a user doesn't exist it will create one.
  
          :param str user_id: identified user's ID
          :param str event_name: event name (e.g. "visit_website")
          :param dict event_properties: properties that describe the event's details
          :param dict headers: custom request headers (if isn't set default values are used)
          :param str endpoint_url: where to send the request (if isn't set default value is used)
          :return: Response