Can I use Python asyncio to slice and save DataFrame in a loop?

As the title says - is it possible to write an asyncio event loop that will slice DataFrame by unique values in a certain column and save it on my drive? And maybe more importantly - is it faster?

What I've tried is something like this:

async def a_split(dist,df):
    temp_df = df[df.district == dist]
    await temp_df.to_csv('{}.csv'.format(d))

async def m_lp(df):
    for dist in df.district.unique().tolist():
        await async_slice(dist,df)

loop = asyncio.get_event_loop()

loop.run_until_complete(m_lp(dfTotal))  
loop.close() 

But I'm getting a following error:

TypeError: object NoneType can't be used in 'await' expression

If it's not obvious from my attempt, I'm very new to asyncio and I'm not sure how it works. Apologies if this is a stupid question.

If asyncio is not a good tool for the job - is there a better one?

Edit:

Full traceback below:

    ---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-22-2bc2373d2920> in <module>()
      2 loop = asyncio.get_event_loop()
      3 
----> 4 loop.run_until_complete(m_lp(dfTotal))
      5 loop.close()

C:\Users\5157213\AppData\Local\Continuum\Anaconda3\envs\python36\lib\asyncio\base_events.py in run_until_complete(self, future)
    464             raise RuntimeError('Event loop stopped before Future completed.')
    465 
--> 466         return future.result()
    467 
    468     def stop(self):

<ipython-input-20-9e91c0b1b06f> in m_lp(df)
      1 async def m_lp(df):
      2     for dist in df.district.unique().tolist():
----> 3         await a_split(dist,df)

<ipython-input-18-200b08417159> in a_split(dist, df)
      1 async def a_split(dist,df):
      2     temp = df[df.district == dist]
----> 3     await temp.to_csv('C:/Users/5157213/Desktop/Portfolio/{}.csv'.format(dist))

TypeError: object NoneType can't be used in 'await' expression