feat(index): ➕ arithmetic addition

[cmp0xff]

It seems that #1347 requires a series of changes, albeit not in the sense of a Pandas Series. This PR could be a good place to start.

• Tests added: Please use assert_type() to assert the type of any return value

[Dr-Irv]

Generally looks good.

I think you can also remove __add__() and __radd__() from IndexOpsMixin because only Index and Series use IndexOpsMixin as a subclass, and now the definitions will reside in class Series and class Index .

I was thinking there might be a way to just put all the operators in IndexOpsMixin, but the challenge there is that Series.__add__(Series) returns a Series at runtime, but Index.__add__(Series) also returns a Series at runtime, so by not allowing Series as a parameter to Index.__add__(), the type checker will revert to the proper overload for Series.__radd__()

[Dr-Irv]

I think you can also remove __add__() and __radd__() from IndexOpsMixin because only Index and Series use IndexOpsMixin as a subclass, and now the definitions will reside in class Series and class Index .

[cmp0xff]

• There is no __add__() or __radd__() in IndexOpsMixin
• There are __add__() and __radd__() in OpsMixin, which I removed in 8a0dcbd. I feel like it is a good idea. There are arithmetic operations that break the pattern -> Self, e.g. Series[Timestamp] - Series[Timestamp]. Removing such definitions may help resolving the conflicts, which still persist in my effort to merge main into refactor: #718 only drop TimestampSeries #1274.

[Dr-Irv]

• There is no __add__() or __radd__() in IndexOpsMixin
• There are __add__() and __radd__() in OpsMixin, which I removed in 8a0dcbd. I feel like it is a good idea. There are arithmetic operations that break the pattern -> Self, e.g. Series[Timestamp] - Series[Timestamp]. Removing such definitions may help resolving the conflicts, which still persist in my effort to merge main into refactor: #718 only drop TimestampSeries #1274.

My mistake - I meant OpsMixin

[Dr-Irv]

thanks @cmp0xff