How to access Task.isBackPressured() from a SourceFunction?

[Darren Whobrey]

Hi, is there a way for the UDF of a source function, extended from 
RichParallelSourceFunction, to access its Task instance, so as to call 
Task.isBackPressured()?
I'm trying to give priorities to different input sources that need to be 
managed from within the same source function and want to stop reading from one 
source according to a utilization statistic that is partially based on whether 
there is backpressure.
Thank you!