code: def get_output_var_names(self):
          
          # Return all the variables that aren't input variables
          all_vars = list(self.species_name_map.keys())
          output_vars = list(set(all_vars) - set(self.input_vars))
          # Re-map to outside var names if needed
          for idx, var in enumerate(output_vars):
              if self._map_in_out(var) is not None:
                  output_vars[idx] = self._map_in_out(var)
          return output_vars
docs: Return a list of variables names that can be read as output.
  
          Returns
          -------
          var_names : list[str]
              A list of variable names that can be read from the outside