Question: Apply Bilinear form for some PDE

I try to get some Bilinear form for some PDE equation  and already i have algorithm by writing in lecture but i can't apply i don't what is mistake i did, and i didn't seen some of this lecture code in maple  like (myint(expr,var))
 i  do upload PIcture of algorithm and example which they get Bilinear form 

Bilinear.mw

thanks for any help

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