API: Make write_brainvision take keyword arguments only

[sappelhoff]

write_brainvision is a long function with many parameters.

Making these parameters keyword only gives us two advantages:

• during development we can in the future move around the parameters as much as we want without breaking anybody's code
• it forces the user to be aware of what argument they pass to which parameter, and errors are less likely

[codecov]

Codecov Report

Merging #57 (65181ad) into master (54da125) will decrease coverage by 2.80%.
The diff coverage is 89.23%.

@@             Coverage Diff             @@
##            master      #57      +/-   ##
===========================================
- Coverage   100.00%   97.19%   -2.81%     
===========================================
  Files            3        3              
  Lines          264      285      +21     
===========================================
+ Hits           264      277      +13     
- Misses           0        8       +8     

Impacted Files	Coverage Δ
pybv/tests/test_bv_writer.py	94.26% <85.71%> (-5.74%)	⬇️
pybv/__init__.py	100.00% <100.00%> (ø)
pybv/io.py	99.37% <100.00%> (-0.63%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 05f6461...65181ad. Read the comment docs.

[hoechenberger]

I guess I would allow for data to be passed by position, but it's a matter of taste I suppose!

Suggested change

	def write_brainvision(*, data, sfreq, ch_names, fname_base, folder_out,
	def write_brainvision(data, *, sfreq, ch_names, fname_base, folder_out,

[sappelhoff]

I would like to keep it all keyword, no positional because I think it leads to a better consistency in this case

[cbrnr]

I'd also prefer the first argument to not be kw-only, but this writer is different enough that I'm also fine with all kw-only (normally the data is the first and the file name the second parameter).

[hoechenberger]

I'm fine with either, just meant to throw in another possibility :)

[sappelhoff]

Okay great, thanks both! I am merging then and following up with a huge API PR that'll better align what we are doing with the BrainVision spec.