How to use the atlassian-jwt.decode function in atlassian-jwt

const installation = await Installation.getForHost(jiraHost)
  res.locals.installation = installation

  req.addLogFields({
    jiraHost: installation.jiraHost,
    jiraClientKey: installation.clientKey
  })

  if (!installation) {
    next(new Error('Not Found'))
  } else {
    try {
      // The JWT contains a `qsh` field that can be used to verify
      // the request body / query
      // See https://bitbucket.org/atlassian/atlassian-connect-express/src/f434e5a9379a41213acf53b9c2689ce5eec55e21/lib/middleware/authentication.js?at=master&fileviewer=file-view-default#authentication.js-227
      jwt.decode(token, installation.sharedSecret)

      next()
    } catch (error) {
      next(new Error('Unauthorized'))
    }
  }
}

type: installation.target_type
      })
      const hasMemberPermission = installation.permissions.members === 'read'
      installationsWithAdmin.push({...installation, admin, hasMemberPermission})
    }
    return installationsWithAdmin
  }

  if (req.query.jwt && req.query.xdm_e) {
    const { jwt: token, xdm_e: jiraHost } = req.query
    const { data: { login } } = await github.users.get()
    try {
      // we can get the jira client Key from the JWT's `iss` property
      // so we'll decode the JWT here and verify it's the right key before continuing
      const installation = await Installation.getForHost(jiraHost)
      const { iss: clientKey } = JWT.decode(token, installation.sharedSecret)

      const { data: { installations } } = (await github.users.getInstallations({}))
      const installationsWithAdmin = await getInstallationsWithAdmin({installations, login})
      const { data: info } = (await client.apps.get({}))
      return res.render('github-configuration.hbs', {
        csrfToken: req.csrfToken(),
        installations: installationsWithAdmin,
        info,
        jiraHost,
        clientKey
      })
    } catch (err) {
      // If we get here, there was either a problem decoding the JWT
      // or getting the data we need from GitHub, so we'll show the user an error.
      req.log.error(err)
      return next(err)