consume method not defined error

Hello,

I am working with Gnuradio 3.8. 

In response to my recent question, I think I found out why my program ran away in an infinite loop. It was because I was not consuming the inputs. So at the end of the loop in the general_work method when I used all the incoming data, I added the following line:

consume(0,len(input_items[0])

Gnuradio seems to have a problem with this and issues an error that the consume method was not defined. How can I fix this? 

Thank you!

Regards,

George