left not inner join

[ryandawsonuk]

Here the instructs say to use a left join:

https://github.com/ryandawsonuk/exercise-ev-databricks/blob/54cfe9ce55904d92da6808bd26e28a0210834be8/batch-processing-gold-2/Batch%20Processing%20-%20Gold%20-%20Solutions.py#L94

But the solution uses an inner join. They actually give the same results as it happens that all requests do have responses. But conceptually I think a left join is intended