Send --dev_samples to Artman via additional arguments to gapic.{lang}_library

[tswast]

I'd like to be able to generate Python code samples via synthtool, but as of googleapis/gapic-generator#2625, this requires an additional --dev_samples argument to artman.

I see that Artman.run accepts an arbitrary number of additional flags to artman via

synthtool/synthtool/gcp/artman.py

Line 70 in c258635

map(str, ["artman", "--local", "--config", config, "generate"] + list(args))

but, there is no way to pass extra parameters from gapic.py_library.

synthtool/synthtool/gcp/discogapic_generator.py

Line 94 in c258635

output_root = artman.Artman().run(

[tswast]

I see a couple of alternatives to solving this issue:

• Add additional artman args list as a parameter to py_library. Then, set additional_artman_args=["--dev_samples"] in my synth.py file to enable sample generation.
• Add a parameter specifically for generating samples, e.g. include_samples=True.

My preference is to add additional_artman_args, but maybe there's a reason for adding separate parameters per artman flag?