fix(GPHedge): replace list with sequence

[phi-friday]

Given the use case below, it seems that base_acquisitions in GPHedge can have multiple types of AcquisitionFunction.

BayesianOptimization/tests/test_acquisition.py

Line 276 in 10ef3be

acq = acquisition.GPHedge(base_acquisitions=base_acquisitions)

However, the type args in list are fixed, so they do not allow such a situation.
Therefore, we need to change to Sequence, which allows args with covariant=True.
I was going to ignore it because it's related to generics,
but it seemed necessary for the use case you're considering, so I fixed it.

Note

This is not a complete description.
But I think it will help you understand why the error is occurring.

• list[T: AcquisitionFunction]: All elements in list are T.

correct case: [UpperConfidenceBound] does belong to list[UpperConfidenceBound].(Also, UpperConfidenceBound is a subclass of AcquisitionFunction.)
error case: [UpperConfidenceBound, ProbabilityOfImprovement] does not belong to any of the three sets list[AcquisitionFunction], list[UpperConfidenceBound], or list[ProbabilityOfImprovement].

• Sequence[T_co: AcquisitionFunction]: Every element in Sequence is either T_co or a subclass of T_co.

[UpperConfidenceBound, ProbabilityOfImprovement] does not belong to Sequence[UpperConfidenceBound] or Sequence[ProbabilityOfImprovement], but it does belong to Sequence[AcquisitionFunction].

[till-m]

Thanks for your contribution!