Groupby Multiprocessing Speeding Up

import multiprocessing

from joblib import Parallel, delayed

def applyParallel(dfGrouped, func):

    retLst = Parallel(n_jobs=multiprocessing.cpu_count())(delayed(func)(group) for name, group in dfGrouped)

    return pd.concat(retLst)

df_result = applyParallel(df.groupby(['code' 'year']), apply_function)