[Node.js] - Unclear what "inventory" is in Transactions example

cluster.transactions().run(async (ctx) => {

  const st = 'SELECT * FROM hotel WHERE country = $1'

  const qr = await ctx.query(st, {

    scope: inventory,

    parameters: ['United Kingdom'],

  })

  for (let row in qr.rows) {

    // do something

  }

})