How can I verify the Beam graph after Coders are inferred

[Reuven Lax]

Hi,

I want to be able to write a verification phase that asserts that input and
output schemas for all ParDos match up properly. The only place I can see
to do that today is in expand(), however this does not work as Coders may
not be fully known when expand is called (remember Schemas are implemented
as a special type of Coder today). For example:

p.apply(ParDo.of(MyDoFn))
  .SetCoder(FooCoder());

FooCoder is not known yet when expand is called for the ParDo.

Is there any place in Beam today where I could set up such a verification
pass?

Reuven