[Feature Request][python]: Better typing support for TimestampedValue

[jonathanasdf]

What would you like to happen?

Currently transforms that return a TimestampedValue need to be typed as plain "TimestampedValue" rather than generic "TimestampedValue[T]" so all underlying information about what type is being wrapped is lost.

Issue Priority

Priority: 3

Issue Component

Component: sdk-py-core

[TheNeuralBit]

Let me re-state to make sure I understand the ask. You're saying that TimestampValue is not a generic type, but it should be?

[jonathanasdf]

Sorry - yes that is a good rephrasing.

[TheNeuralBit]

Got it, I think this would be a relatively straightforward change - just refactor TimestampedValue to inherit from Generic. In order for it to have an effect on beam typehints, we'd also want to adjust DoFn.default_type_hints to extract the element type from the generic TimestampedValue (and we should do the same for WindowedValue).

[liferoad]

.take-issue