feat(protocol-designer): emit Python for aspirate command

[ddcc4]

Overview

This implements Python code generation for the PD atomic aspirate command. AUTH-1094

The generated code looks like this:

pipette_left.aspirate(
    volume=75,
    location=well_plate_2["B2"].bottom(z=1),
    rate=716 / pipette_left.flow_rate.aspirate,
)

Test Plan and Hands on Testing

Added unit tests.

I also took the generated code and added it to a Python protocol and confirmed that it is understandable by simulate.

Review requests

PD has its own code to load the default flow rates for a particular pipette/tip/volume:

opentrons/protocol-designer/src/utils/index.ts

Lines 211 to 215 in 8fe0be1

	export function getMatchingTipLiquidSpecs(
	pipetteEntity: PipetteEntity,
	volume: number,
	tiprack: string
	): SupportedTip {

I was trying really hard to use those default flow rates to compute the ratio in JavaScript to pass to aspirate(rate=...). E.g., if we knew that the default flow rate is 700 uL/s, and the PD user wants a flow rate of 350 uL/s, I wanted to generate code like aspirate(rate=0.5).

But that turned out to be unworkable. PD has a very specific algorithm for picking the default flow rates, which is not the same as what the PAPI implements. Furthermore, we discovered that the current implementation for default flow rates in the PAPI is just wrong.

So in this PR, I had to emit an explicit division expression to generate the aspirate(rate=...) argument.

Risk assessment

Low. Python export in PD is not available to external users yet.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 25.64%. Comparing base (7fdb309) to head (ed9425d).
Report is 2 commits behind head on edge.

Additional details and impacted files

@@            Coverage Diff             @@
##             edge   #17594      +/-   ##
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- Coverage   25.64%   25.64%   -0.01%     
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  Files        2841     2841              
  Lines      218631   218730      +99     
  Branches    17944    17944              
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+ Hits        56077    56092      +15     
- Misses     162539   162623      +84     
  Partials       15       15              

Flag	Coverage Δ
protocol-designer	18.88% <100.00%> (+0.01%)	⬆️
step-generation	4.38% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...-generation/src/commandCreators/atomic/aspirate.ts	89.65% <100.00%> (+0.71%)	⬆️

... and 4 files with indirect coverage changes

[ncdiehl11]

this will effectively stick the division expression into the Python rate arg value, right? is that what we want?

[ncdiehl11]

sorry, just re-read the PR description. makes sense to me.