code: public String toSource(final JSModule module) {
      return runInCompilerThread(
          () -> {
            List<CompilerInput> inputs = module.getInputs();
            int numInputs = inputs.size();
            if (numInputs == 0) {
              return "";
            }
            CodeBuilder cb = new CodeBuilder();
            for (int i = 0; i < numInputs; i++) {
              Node scriptNode = inputs.get(i).getAstRoot(Compiler.this);
              if (scriptNode == null) {
                throw new IllegalArgumentException("Bad module: " + module.getName());
              }
              toSource(cb, i, scriptNode);
            }
            return cb.toString();
          });
    }
docs: Converts the parse tree for a module back to JS code.