This the format used by operator >> of the CGAL::Polygon_with_holes_2 template class
used in these examples.
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outer_boundary_number_of_vertices
outer_boundary_x1 outer_boundary_y1
outer_boundary_x2 outer_boundary_y2
...
outer_boundary_xN outer_boundary_yN
numer_of_holes
hole_1_number_of_vertices
hole_1_x1 hole_1_y1
hole_1_x2 hole_1_y2
...
hole_1_xN hole_1_yN
....
hole_2_number_of_vertices
hole_2_x1 hole_2_y1
hole_2_x2 hole_2_y2
...
hole_2_xN hole_2_yN