Refactor of flow tools - Verification of XZCorrections objects

[matulni]

This PR adds a new method :func: XZCorrections.check_well_formed to verify the correctness of XZ-corrections objects.

A correct XZCorrections instance verifies the following properties:
- Keys of the correction dictionaries are measured nodes, i.e., a subset of $O^c$.
- Corrections respect the partial order.
- The first layer of the partial order contains all the output nodes if there are any.
- The partial order contains all the nodes (without duplicates) and it does not have empty layers.

This PR builds on the exception classes introduced in #378. We detail next the full exception landscape.

---
config:
layout: elk
elk:
mergeEdges: false
nodePlacementStrategy: LINEAR_SEGMENTS
---
flowchart TD
a0(**Exception**)
m0(**XZCorrectionsError**)
n0(**FlowError**)
n1(FlowGenericError)
n2(FlowPropositionError)
n3(FlowPropositionOrderError)
n4(PartialOrderError)
n5(PartialOrderLayerError)
m1(XZCorrectionsOrderError)
m2(XZCorrectionsGenericError)
a0 --> m0
a0 --> n0
m0 --POEReason--> n4
m0 --POLEReason--> n5
m0 --XZCOEReason--> m1
m0 --XZCGEReason--> m2
n0 --FGEReason--> n1
n0 --FPEReason--> n2
n0 --FPOEReason--> n3
n0 --POEReason--> n4
n0 --POLEReason--> n5

Loading

• Arrows indicate inheritance (from parent to child).

• "Reasons" (XZCorrectionsOrderErrorReason, etc.) are Enum classes.

• New error subclasses:

  • XZCorrectionsOrderError
    • Errors in XZ-corrections objects concerning the correction dictionaries and the partial order.
    • Additional parameters:
      • node
      • correction_set
      • past_and_present_nodes
  • XZCorrectionsGenericError
    • Generic errors.
    • Does not require additional parameters.

[emlynsg]

Can this be removed?

[matulni]

Yes, thanks! Done in c13057d

[emlynsg]

Should this be

layer_idx=len(self.partial_order_layers) -shift

?

[matulni]

mmm, I don't think so... shift removes the first element of self.partial_order_layers if it contains output nodes. We initialize layer_idx to the last layer index (that is, the length of the list minus 1, whether we removed the first element or not) to keep track of the layer index when iterating in reverse order. I added a comment in 095a2de.

[mgarnier59]

Nothing to add! Thanks for the work.

[codecov]

Codecov Report

❌ Patch coverage is 78.75000% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.90%. Comparing base (92c9766) to head (88f6ece).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
graphix/flow/exceptions.py	68.18%	14 Missing ⚠️
graphix/flow/core.py	91.66%	3 Missing ⚠️

Additional details and impacted files

@@ Coverage Diff @@## master #385 +/- ##
==========================================
- Coverage 85.99% 85.90% -0.10% 
==========================================
Files 45 45 Lines 6471 6540 +69 ==========================================
+ Hits 5565 5618 +53 - Misses 906 922 +16 

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[thierry-martinez]

Nice work! Thanks.