> +accepts one :term:`positional argument` (``voltage``) and three
> +:term:`keyword arguments <keyword argument>` (``state``, ``action``,
> +and ``type``).  
>
> This is simply false. An argument for voltage is required, the other
> three are optional. I suggest something like the followinga:

That part refers to the function signature, not the function call.  I tried to avoid using the term "function signature" to avoid introducing yet another term, but maybe the two things should be separated a bit more.

I also tried to avoid the use of 'parameters' (the 'names' in the function signature) and 'arguments' (the actual values passed to the function when it's called) to keep the things simple and also because not everyone agrees on this terminology.

Would adding 'required' before 'positional' and 'optional' before 'keyword arguments' be ok?