docs: def return_single_convert_numpy_base(dbpath, folder_path, set_object, object_id, converter, add_args=None):
      """
      Generic function which converts an object specified by the object_id into a numpy array and returns the array,
      the conversion is done by the 'converter' function
  
      Parameters
      ----------
      dbpath : string, path to SQLite database file
      folder_path : string, path to folder where the files are stored
      set_object : object (either TestSet or TrainSet) which is stored in the database
      object_id : int, id of object in database
      converter : function, which takes the path of a data point and *args as parameters and returns a numpy array
      add_args : optional arguments for the converter (list/dictionary/tuple/whatever). if None, the
      converter should take only one input argument - the file path. default value: None
  
      Returns
      -------
      result : ndarray
      """
      engine = create_engine('sqlite:////' + dbpath)
      session_cl = sessionmaker(bind=engine)
      session = session_cl()
      tmp_object = session.query(set_object).get(object_id)
      session.close()
      if add_args is None:
          return converter(join(folder_path, tmp_object.path))
      else:
          return converter(join(folder_path, tmp_object.path), add_args)