Implement DataSource.get_contiguous_time_periods()

[JackKelly]

Pull Request

Description

This is a bite-sized part of a larger issue (#223).

The ultimate aim of #223 is to change the way nowcasting_dataset computes the set available datetimes across all DataSources.

This PR basically just implements one function and its test: DataSource.get_contiguous_time_periods().

There are a few other little bits-and-bobs (which, if I was being really well behaved, would be in separate PRs!)

• There are also some small formatting tweaks (mostly fixing lines > 100 characters).
• Removed the ancient "temporary code" from DataSource.get_locations_for_batch() which could silently create nasty bugs in our prepared data batches!

How Has This Been Tested?

The PR implements a new unit-test. All tests pass.

• No
• Yes

Checklist:

• My code follows OCF's coding style guidelines
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked my code and corrected any misspellings

[peterdudfield]

Looks good, very good to break it into a small PR.

[peterdudfield]

worth adding a logging statement?

[JackKelly]

Good question! TBH, if someone tries to call this function in the wrong context then that suggests a major mistake, so we probably want the code to blow up noisily (i.e. to throw an exception). So, if it's OK, I'll leave it like this for now, and we can see how we get on?