Add __repr__ to Region and CacheMiss utility classes (fixes #1219)

[Yashsingh045]

Summary

Fixes #1219.

The Region class had a useful __str__ but no __repr__, meaning it displayed as an unhelpful <malariagen_data.util.Region object at 0x...> inside lists, dicts, and REPL sessions. Similarly CacheMiss was a bare Exception subclass with no message formatting.

Changes

malariagen_data/util.py

Region.__repr__ — returns a constructor-style string:

>>> Region('2L', 100_000, 200_000)
Region('2L', 100000, 200000)
>>> [Region('2L'), Region('3R', 10, 20)]
[Region('2L', None, None), Region('3R', 10, 20)]

(the existing __str__ format is unchanged: '2L:100,000-200,000')

CacheMiss — adds a docstring, default message, and __repr__:

>>> str(CacheMiss())
'Cache miss: requested item not found in cache.'
>>> str(CacheMiss('my_key'))
"Cache miss for key: 'my_key'"
>>> repr(CacheMiss('my_key'))
"CacheMiss('my_key')"

tests/test_util.py (new file)

Unit tests covering all the above behaviours.

Testing

All existing tests continue to pass. New tests added in tests/test_util.py.

[Yashsingh045]

hey @jonbrenas ,
Could you please review this PR?

[Yashsingh045]

hey @jonbrenas ,
I have fixed the lint error.
Could you please review this PR?

[Yashsingh045]

Hi @jonbrenas ,
Just a gentle reminder, Please review this PR when you have time.
Thanks