Create simple box device for memory input/output

[callumforrester]

This PR just illustrates an idea that came up in discussion with @abbiemery, not necessarily to be merged.

The envisioned use of this class is where you wish to simulate a network interface but the internal hardware logic is either not needed or very simple. A custom adapter can be made for the network interface and can simply read and write to an IoBox. I wondered if a lot of people would write devices like this and if it would make sense for tickit to provide a simple helper device.

Any thoughts welcome.

[codecov]

Codecov Report

Merging #70 (448ce61) into master (ada93e7) will increase coverage by 0.14%.
The diff coverage is 97.22%.

@@            Coverage Diff             @@
##           master      #70      +/-   ##
==========================================
+ Coverage   92.32%   92.47%   +0.14%     
==========================================
  Files          44       45       +1     
  Lines        1186     1222      +36     
==========================================
+ Hits         1095     1130      +35     
- Misses         91       92       +1     

Impacted Files	Coverage Δ
src/tickit/devices/iobox.py	97.22% <97.22%> (ø)

[abbiemery]

For context my use case is for creating devices/etc to be used in system tests in Artemis (ophyd-bluesky). They just need to be set and read from a network and do not need to talk to each other. I'm sure I'll see soon enough if I end up making a lot of these.

[garryod]

This seems like a really nice helper, I reckon it's a good addition to the framework.

It may be useful to add the option of outputting select keys at update time, thoughts?

[callumforrester]

I considered outputting keys at update time, what do you think the best solution is out of these?

1. Have a non-total TypedDict with untyped fields
2. Have a single field whose value is a dictionary/dataclass
3. Write fields you wish to output manually in Inputs of subclasses

Or indeed, do you have any other ideas?

[garryod]

I considered outputting keys at update time, what do you think the best solution is out of these?

1. Have a non-total TypedDict with untyped fields
2. Have a single field whose value is a dictionary/dataclass
3. Write fields you wish to output manually in Inputs of subclasses

Or indeed, do you have any other ideas?

A partial TypedDict with untyped fields seems the best without having the device grow arms and legs. Ultimately we accept that we sacrifice static type checking by using a device like this. It may however be worth considering adding run-time type checking if the user enters a mapping of outputs and their type in the config yaml, though with how easy it is to write a custom device this seems unlikely to be necessary, especially considering the opacity of such an implementation

[garryod]

Would be good to include a system test to cover the ComponentConfig

[abbiemery]

Looks good to me.