math.addChild(pieces);
fd.setMath(math);
System.out.println(math.toMathML());
Species species = m.createSpecies("spec");
Reaction r = m.createReaction("r");
r.addReactant(new SpeciesReference(species));
KineticLaw kl = new KineticLaw(level, version);
math = new ASTNode(fd, kl);
math.addChild(new ASTNode(species, kl));
math = ASTNode.times(math, new ASTNode(3.7, 8, kl));
kl.setMath(math);
r.setKineticLaw(kl);
System.out.println(math.toMathML());
try {
new SBMLWriter().write(doc, System.out);