Couplings method is called with array instead of float

[felixhekhorn]

Can you please have a look to the deprecation warning from numpy here

specifically all the

/home/runner/work/eko/eko/src/eko/couplings.py:691: DeprecationWarning: Conversion of an array with ndim > 0 to a scalar is deprecated, and will error in future. Ensure you extract a single element from your array before performing this operation. (Deprecated NumPy 1.25.)
    key = (float(a_ref[0]), float(a_ref[1]), nf, nl, scale_from, float(scale_to))

look very suspicious - someone is calling the method with scale_to not being a float, which is clearly wrong

It might be a badly written test.