How to question
Hi there,

I want to select all the rows in my data frame where 'finished_processing_date' is not null.

I know I can do something like this to count the null fields

```python
df_not_finished_processing = df[df['finished_processing_date'].isnull()];
df_not_finished_processing.count()
```

but what about doing the opposite? Selecting all rows that the field is not null.