code: def output_key_name(self, input_key: str, output_hist: Hist, projection_name: str, **kwargs) -> str:
          
          return projection_name
docs: Returns the key under which the output object should be stored.
  
          Note:
              This function is just a basic placeholder which returns the projection name
              and likely should be overridden.
  
          Args:
              input_key: Key of the input hist in the input dict
              output_hist: The output histogram
              projection_name: Projection name for the output histogram
              kwargs: Projection information dict combined with additional arguments passed to
                  the projection function.
          Returns:
              Key under which the output object should be stored. By default, it returns the
                  projection name.