API Documentation issues

Hello there, I'm using Fslex/Fsyacc for a complex language, and I'm missing doc information.

Typically, I don't get how to use  ParseErrorContext. When can I get the value ?

Also ParseHelpers seem to provide the functions that use ParseErrorContext, but how redefine them ? 
There is no example in the doc on how to use them.

This is really blocking me.

Thanks for your help!
