gistfile1.txt

In [8]: mesh._base_mesh.topology.interior_facets.local_facet_dat.data
Out[8]: 
array([[ 0, 19],
       [ 2,  2],
       [ 0, 17],
       [ 0, 16],
       [ 2,  2],
       [ 2,  2],
       [ 0, 13],
       [ 0, 12],
       [ 2,  2],
       [ 2,  2],
       [ 0, 21],
       [ 0, 22],
       [ 2,  2],
       [ 2,  2],
       [36, 25],
       [35, 26],
       [ 2,  2],
       [ 2,  2],
       [ 0, 29],
       [ 0, 30],
       [ 2,  2],
       [ 2,  2],
       [ 0, 43],
       [ 0, 76],
       [ 2,  2],
       [ 2,  2],
       [ 0, 47],
       [ 0, 72],
       [ 2,  2],
       [ 2,  2],
       [71, 51],
       [52, 68],
       [ 2,  2],
       [ 2,  2],
       [ 0, 55],
       [ 0, 64],
       [ 2,  2],
       [ 2,  2],
       [ 0, 59],
       [ 2,  2]], dtype=uint32)