GROMACS

Helper functions that create gmxapi operations from Python functions accept "input" and "output" key word arguments. "input" is also the name of a Python built-in function. I don't know anyone who uses "input", but it is masked in the scope of such functions. We could change the names of these key word arguments to avoid masking the built-in symbol. I expect the impact of not changing it is very low, but the impact of changing is lowest if we do it sooner than later.

Note that "output" appears in a few other places. Since the argument passed as "output" is not semantically identical to the the attributes named "output" that appear elsewhere, I think it might actually be clearer to have a different name than the key word argument, but I'm not sure whether a one letter difference helps or hurts.

Feedback requested for priority, options, and target version.