Question about black formatting

I'm trying to run the black formatter on `_lightfm_fast.pyx.template`, but am getting a parsing error. According to psf/black#359 it doesn't look like black supports cython yet, so how do I enforce formatting on this file?

```
/Users/npow/anaconda/bin/black /Users/npow/code/lightfm/lightfm/_lightfm_fast.pyx.template
error: cannot format /Users/npow/code/lightfm/lightfm/_lightfm_fast.pyx.template: Cannot parse: 6:8: cimport cython.operator.dereference as deref
Oh no! \U0001f4a5 \U0001f494 \U0001f4a5
1 file failed to reformat.

Process finished with exit code 123
```

Start with `_lightfm_fast.pyx.template` and reproduce the Black parsing error shown in the issue. Investigate the project's existing formatting setup and the documented options for handling this Cython template; done should be a clear, documented way to enforce or intentionally skip formatting for the file.

Written by the indexing model from the issue text.