How to use the traceur.codegeneration function in traceur

traceur.options = o.options;
    traceur.options.sourceMaps = true;
    traceur.options.modules = 'parse';

    var reporter = new traceur.util.ErrorReporter();
    reporter.reportMessageInternal = function(location, kind, format, args) {
      process.stdout.write(JSON.stringify({ err: kind + '\n' + o.file + location }));
      process.exit(0);
    }

    var parser = new traceur.syntax.Parser(reporter, new traceur.syntax.SourceFile(o.file, o.source));
    var tree = parser.parseModule();

    var project = new traceur.semantics.symbols.Project(o.file);
    var transformer = new traceur.codegeneration.ProgramTransformer(reporter, project);
    tree = transformer.transform(tree);

    // generate source
    var sourceMapGenerator = new traceur.outputgeneration.SourceMapGenerator({ file: o.originalFile });
    var opt = { sourceMapGenerator: sourceMapGenerator };

    var source = traceur.outputgeneration.TreeWriter.write(tree, opt);

    process.stdout.write(JSON.stringify({
      source: source,
      sourceMap: opt.sourceMap
    }));
  }
  catch(e) {
    process.stdout.write(JSON.stringify({ err: e.toString() }));
    return process.exit(0);

var traceur = require('traceur');
var ParseTreeTransformer = traceur.codegeneration.ParseTreeTransformer;

// var token = traceur.syntax.TokenType;
// var CONSTRUCTOR = token.CONSTRUCTOR;

var parseToken = traceur.syntax.trees.ParseTreeType;
var PROPERTY_METHOD_ASSIGNMENT = parseToken.PROPERTY_METHOD_ASSIGNMENT;
var MEMBER_EXPRESSION = parseToken.MEMBER_EXPRESSION;
var THIS_EXPRESSION = parseToken.THIS_EXPRESSION;
var BINARY_EXPRESSION = 'BINARY_EXPRESSION';
var EQUAL_EQUAL_EQUAL = traceur.syntax.TokenType.EQUAL_EQUAL_EQUAL;
var CONSTRUCTOR = traceur.syntax.PredefinedName.CONSTRUCTOR;

var VariableDeclarationList = traceur.syntax.trees.VariableDeclarationList;
var VariableStatement = traceur.syntax.trees.VariableStatement;

var Token = traceur.syntax.Token;

// ES5 source transform/transpiler based on the es6ify browserify transform by thlorenz

'use strict';

var traceur            =  require('traceur')
  , compile            =  traceur.codegeneration.Compiler.compile
  , Project            =  traceur.semantics.symbols.Project
  , ProjectWriter      =  traceur.outputgeneration.ProjectWriter
  , SourceFile         =  traceur.syntax.SourceFile
  , format             =  require('util').format
  , path               =  require('path')
  ;

+function initGlobalTraceurOptions() {
  [ 'arrayComprehension'
    , 'arrowFunctions'
    , 'classes'
    , 'defaultParameters'
    , 'destructuring'
    , 'forOf'
    , 'propertyMethods'
    , 'propertyNameShorthand'

var THIS_EXPRESSION = parseToken.THIS_EXPRESSION;
var BINARY_EXPRESSION = 'BINARY_EXPRESSION';
var EQUAL_EQUAL_EQUAL = traceur.syntax.TokenType.EQUAL_EQUAL_EQUAL;
var CONSTRUCTOR = traceur.syntax.PredefinedName.CONSTRUCTOR;

var VariableDeclarationList = traceur.syntax.trees.VariableDeclarationList;
var VariableStatement = traceur.syntax.trees.VariableStatement;

var Token = traceur.syntax.Token;
var propName = traceur.staticsemantics.propName;


var createVariableStatement = traceur.codegeneration.ParseTreeFactory.createVariableStatement;
var createCallExpression = traceur.codegeneration.ParseTreeFactory.createCallExpression;
var createIdentifierExpression = traceur.codegeneration.ParseTreeFactory.createIdentifierExpression;
var createArgumentList = traceur.codegeneration.ParseTreeFactory.createArgumentList;


var ClassFieldParseTree = require('./ast/class_field');

// - rename constructor (name of the class - default Dart constructor)
// - collect fields (set in the constructor) and define them as class fields
function ClassTransformer() {
  ParseTreeTransformer.call(this);

  // Transform multi-var declarations, into multiple statements:
  // var x, y;
  // ==>
  // var x;
  // var y;
  // TODO(vojta): move this into a separate transformer.

f.src.filter(function(filepath) {
    if (!grunt.file.exists(filepath)) {
      grunt.log.warn('Source file "' + filepath + '" not found.');
      return false;
    } else {
      return true;
    }
  }).map(function(filepath) {
    var sourceFile = new traceur.syntax.SourceFile(path.relative(cwd, filepath),
      grunt.file.read(filepath));
    project.addFile(sourceFile);
  });

  currentDir = process.cwd();
  process.chdir(cwd);
  asts = traceur.codegeneration.Compiler.compile(reporter, project);
  process.chdir(currentDir);

  if (reporter.hadError()) {
    grunt.log.error('Compilation error!');
    reporter.errors.forEach(function(e) {
      grunt.log.error(e);
    });
    return false;
  }

  asts.keys().forEach(function(file) {
    var ast, code, treeWriteOpts, sourceMapGenerator;
    var sourceMapDest, sourceMapRoot, sourceMapConfig;     
    var outFile = f.dest;
    var outDir = path.dirname(outFile);