fix axis use for sum

[timmysilv]

User description

Note: This is not critically needed, because users can just pass axis=[x] instead of axis=x and it will work - it's more aesthetic than anything.

Context:
np.sum only accepts ints for the axis, or tuples of ints. We recently updated the backend manager to match numpy by renaming axes to axis, but unexpectedly do not accept a single int as the singular name implies. Even stranger, np.sum(..., axis=[1, 2]) fails because axis must be a tuple and not a list. We cast to tuple internally so that usage is alright with mrmustard.math.sum.

Description of the Change:
Accept single ints as well as sequences of ints.

Benefits:
mrmustard.math.sum better matches the backend library conventions.

Possible Drawbacks:
N/A

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PR Type

Bug fix, Enhancement

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Description

• Updated math.sum to accept single integers for axis.

• Replaced list-based axis arguments with integers or tuples across the codebase.

• Improved compatibility with backend libraries by aligning math.sum behavior.

• Adjusted related tests to reflect the updated axis handling.

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Changes walkthrough 📝

	Relevant files
Bug fix	6 files circuit_components.py Updated `math.sum` calls to use integer `axis`.                    +1/-1      base.py Replaced list-based `axis` with integer in `math.sum`.      +3/-3      array_ansatz.py Fixed `math.sum` usage with integer `axis`.                            +1/-1      polyexp_ansatz.py Replaced list-based `axis` with integer in `math.sum`.      +3/-3      gaussian_integrals.py Updated `math.sum` to use integer `axis`.                                +1/-1      representations.py Fixed `math.sum` usage with integer `axis`.                            +1/-1
Enhancement	3 files backend_manager.py Enhanced `math.sum` to accept int or sequence for `axis`. +3/-3      backend_numpy.py Updated `math.sum` to support int or sequence for `axis`. +1/-1      backend_tensorflow.py Adjusted `math.sum` to handle int or tuple for `axis`.      +1/-1
Tests	1 files test_cft.py Adjusted test to reflect updated `math.sum` behavior.        +1/-1

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⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🏅 Score: 95

🧪 PR contains tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Type Consistency The type hint for axis parameter in sum() method uses both Sequence[int] and tuple[int] across different backend implementations. Consider standardizing the type hints for consistency. def sum(self, array: Tensor, axis: int | Sequence[int] | None = None): r"""The sum of array. Args: array: The array to take the sum of axis (int | Sequence[int] | None): The axis/axes to sum over Returns: The sum of array """ if axis is not None and not isinstance(axis, int): neg = [a for a in axis if a < 0] pos = [a for a in axis if a >= 0] axis = tuple(sorted(neg) + sorted(pos)[::-1]) return self._apply("sum", (array, axis))

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.01%. Comparing base (2bd6489) to head (b5bbba6).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #543      +/-   ##
===========================================
- Coverage    90.05%   90.01%   -0.04%     
===========================================
  Files          102      102              
  Lines         6222     6222              
===========================================
- Hits          5603     5601       -2     
- Misses         619      621       +2     

Files with missing lines	Coverage Δ
mrmustard/lab_dev/circuit_components.py	98.44% <ø> (ø)
mrmustard/lab_dev/states/base.py	96.66% <100.00%> (ø)
mrmustard/math/backend_manager.py	98.17% <100.00%> (ø)
mrmustard/math/backend_numpy.py	100.00% <ø> (ø)
mrmustard/math/backend_tensorflow.py	100.00% <ø> (ø)
mrmustard/physics/ansatz/array_ansatz.py	100.00% <100.00%> (ø)
mrmustard/physics/ansatz/polyexp_ansatz.py	98.57% <100.00%> (ø)
mrmustard/physics/gaussian_integrals.py	99.39% <ø> (ø)
mrmustard/physics/representations.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[ziofil]

thanks!