Integral on only intefaces, not on boundary faces

I tried to implement DG method for the following problem: Find (u_h,p_h)such that [tex]a_h(u_h, v_h) + b_h(v_h, p_h)-b_h(u_h, q_h)+ s_h(p_h, q_h)=\int_\Omega f\cdot v_h\,\forall v_h \in U_h, \forall q_h \in P_h,[/tex]
where [tex]s_h(q_h, r_h):=\sum\limits_{F\in \mathcal{F}^i_h}h_F\int_Fq_hr_h.[/tex]
I used sh*dx(skeleton=True) as in the tutorial to compute the integral on inteface of s_h, but there is a traceback call.

I also attached my .ipynb file. Could you please show me fixed this error or how to compute that integral on only interfaces?
Thank you so much.

Hi dong,

you need to set the dgjumps flag for a DG formulation as described here

Then your code should run through.

Best
Michael

Thank you for your help. The code run smoothly now.