No column specified

[jtinsky]

I'm a spark newbie but I ran the example and it eventually died on line 41 I think because no column was specified. I added the "population" alias and still got the error below.

Traceback (most recent call last): File "/opt/application/main.py", line 41, in medianDF = kDF.median().withColumn('population') File "/opt/conda/lib/python3.8/site-packages/databricks/koalas/series.py", line 6153, in getattr raise AttributeError("'Series' object has no attribute '{}'".format(item)) AttributeError: 'Series' object has no attribute 'withColumn'

https://github.com/datamechanics/examples/blob/fd391c69559f756d9341f357830d38e54749c91f/pyspark-example/main.py#L41