@step decorator to easily create steps

[gabrielmbmb]

Add a @step decorator allowing to easily create new steps.

@step(inputs=["instruction"], outputs=["generation"])
def MyStep(input: StepInput, runtime_param1: RuntimeParameter[int], runtime_param2: RuntimeParameter[str] = "hello"0 -> StepOutput:
    ...

with Pipeline():
    step = MyStep(name="my_step")

The decorator will create a subclass of Step programatically that can be used in a Pipeline.