code: function render(file, data, outputDir) {
    if (!argv.unsafe && path.extname(file) === '.html')
      return console.error(chalk.red(file + ': To use .html as source files, add --unsafe/-u flag'))
  
    env.render(file, data, function(err, res) {
      if (err) return console.error(chalk.red(err))
      var outputFile = file.replace(/\.\w+$/, '') + '.html'
      if (outputDir) {
        outputFile = path.resolve(outputDir, outputFile)
        mkdirp.sync(path.dirname(outputFile))
      }
      console.log(chalk.blue('Rendering: ' + file))
      fs.writeFileSync(outputFile, res)
    })
  
  }
docs: Render one file