Tuple-related type hints

[alecandido]

A quite trivial fix, just because I noticed it while working on Qibolab.

Tuples are immutable containers, thus the plain type hint is dedicated to the fixed size ones. To return a variable size tuple, tuple[MyType, ...] is required. tuple[MyType] is describing a 1-element tuple, whose element has type MyType.

Conversely, lists and dictionaries are mutable, and their basic and only type hints are not imposing any restriction on the length.

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[renatomello]

These changes would have to be applied throughout the entire module, no?

[alecandido]

These changes would have to be applied throughout the entire module, no?

Yes, and I'm planning to do a consistent review of types at some point (there are further improvements/fixes to add). But these methods are very common, so I decided to fix these immediately, instead of delaying them with everything else.

Moreover, I checked that most of the usage of Tuple[] are consistent, since they refer to fixed length tuples. There might be some further occurrences just in the quantum_info module.

[alecandido]

@renatomello: for me, this PR is ready as it is. But if you want to do something else, we can discuss (though I will not commit soon to much more, that's why I'd prefer to open a new one later on).

[BrunoLiegiBastonLiegi]

I wasn't aware of the Tuple[type, ...] syntax, thanks for pointing out.