code: def create_activity(self, activity_name, desc=None, started_on=None, ended_on=None):
          
          data = {
              "name": activity_name,
              "description": desc,
              "started_on": started_on,
              "ended_on": ended_on
          }
          return self._post("/activities", data)
docs: Send POST to /activities creating a new activity with the specified name and desc.
          Raises DataServiceError on error.
          :param activity_name: str name of the activity
          :param desc: str description of the activity (optional)
          :param started_on: str datetime when the activity started (optional)
          :param ended_on: str datetime when the activity ended (optional)
          :return: requests.Response containing the successful result