How to use the @serverless/core.utils.writeFile function in @serverless/core

inputs.cors || null,
      inputs.protocol
    )

    // Build environment variables
    if (inputs.env && Object.keys(inputs.env).length && inputs.code.root) {
      this.context.status(`Bundling environment variables`)
      this.context.debug(`Bundling website environment variables.`)
      let script = 'window.env = {};\n'
      inputs.env = inputs.env || {}
      for (const e in inputs.env) {
        // eslint-disable-line
        script += `window.env.${e} = ${JSON.stringify(inputs.env[e])};\n` // eslint-disable-line
      }
      const envFilePath = path.join(inputs.code.root, 'env.js')
      await utils.writeFile(envFilePath, script)
      this.context.debug(`Website env written to file ${envFilePath}.`)
    }

    // If a hook is provided, build the website
    if (inputs.code.hook) {
      this.context.status('Building assets')
      this.context.debug(`Running ${inputs.code.hook} in ${inputs.code.root}.`)

      const options = { cwd: inputs.code.root }
      try {
        await exec(inputs.code.hook, options)
      } catch (err) {
        console.error(err.stderr) // eslint-disable-line
        throw new Error(
          `Failed building website via "${inputs.code.hook}" due to the following error: "${err.stderr}"`
        )

this.context.debug(`Configuring bucket ${inputs.bucketName} for website hosting.`)
    await configureBucketForHosting(s3, inputs.bucketName)

    // Build environment variables
    inputs.env = inputs.env || {}
    if (Object.keys(inputs.env).length && inputs.code.root) {
      this.context.status(`Bundling environment variables`)
      this.context.debug(`Bundling website environment variables.`)
      let script = 'window.env = {};\n'
 
      for (const e in inputs.env) {
        // eslint-disable-line
        script += `window.env.${e} = ${JSON.stringify(inputs.env[e])};\n` // eslint-disable-line
      }
      const envFilePath = path.join(inputs.code.root, 'env.js')
      await utils.writeFile(envFilePath, script)
      this.context.debug(`Website env written to file ${envFilePath}.`)
    }

    // If a hook is provided, build the website
    if (inputs.code.hook) {
      this.context.status('Building assets')
      this.context.debug(`Running ${inputs.code.hook} in ${inputs.code.root}.`)

      const options = { 
        cwd: inputs.code.root,
        // Merge input & process env variables to be available for hooks execution
        env: Object.assign(process.env, inputs.env),
      }

      try {
        await exec(inputs.code.hook, options)