Add test to demonstrate usage of proposed mathId() function. Will not compile.
Add test to demonstrate usage of proposed mathId() function. Will not compile.

cellml/libcellml,cellml/libcellml,hsorby/libcellml,nickerso/libcellml,nickerso/libcellml,cellml/libcellml,hsorby/libcellml,hsorby/libcellml,cellml/libcellml,nickerso/libcellml,hsorby/libcellml,nickerso/libcellml