a more generalized solution for cif parsing

[anupam-banerjee]

Fix _getBiomoltrans to robustly parse mmCIF oper_expression: accept alphanumeric op IDs (X0, P), expand ranges anywhere (incl. inside lists), and handle products of groups like (X0)(1-5).

[jamesmkrieger]

looks good and I've tested pieces and it seems to work as expected.

It would be good to have a unit test for this too

[AnthonyBogetti]

Let's come up with a unit test for this before merging.

[AnthonyBogetti]

test_ciffile.py
Here is a modified test_ciffile.py to cover the changes in this PR. @anupam-banerjee, please test on your code and if it works, let's merge this.

[jamesmkrieger]

test_ciffile.py Here is a modified test_ciffile.py to cover the changes in this PR. @anupam-banerjee, please test on your code and if it works, let's merge this.

Why do we need a modified version? Surely it’s better to have an additional one and keep checking that old ones work too?

[AnthonyBogetti]

test_ciffile.py Here is a modified test_ciffile.py to cover the changes in this PR. @anupam-banerjee, please test on your code and if it works, let's merge this.

Why do we need a modified version? Surely it’s better to have an additional one and keep checking that old ones work too?

The test_ciffile.py file itself is modified, but all existing tests should have been left untouched. The new test to cover the changes in this PR was added to the end of the file. Sorry, I should have been more clear.