How to use the faunadb.query.Map function in faunadb

queryPlayerItems(players) {
    const refs = players.map((p) => p.ref);
    console.log("queryPlayerItems", refs);
    return this.client.query(
      q.Map(refs, (ref) => q.Select("data", q.Map(
        q.Paginate(q.Match(q.Index("items_by_owner"), ref)),
        (row) =>  q.Get(row)
      )))
    );
  }

listPurchases() {
    return this.client.query(
      q.Map(
        q.Paginate(q.Match(q.Index("purchases")), {before : null}),
        (row) => q.Let({row:q.Get(row)},
          q.Let({
            buyer : q.Get(q.Select(["data","buyer"], q.Var("row"))),
            seller : q.Get(q.Select(["data","seller"], q.Var("row"))),
            price : q.Select(["data","price"], q.Var("row")),
            item : q.Get(q.Select(["data","item"], q.Var("row")))
          },
          {
            buyer : q.Select(["data","name"], q.Var("buyer")),
            seller : q.Select(["data","name"], q.Var("seller")),
            price : q.Var("price"),
            label : q.Select(["data","label"], q.Var("item")),
            key : q.Select(["ref"], q.Var("row"))
          }
        ))

queryItemsForSale() {
    return this.client.query(
      q.Map(
        q.Paginate(q.Match(q.Index("items_for_sale"), true)),
        (row) =>
        q.Let({doc : q.Get(row)}, {
          ref : q.Select(["ref"], q.Var("doc")),
          data : {
            label : q.Select(["data","label"], q.Var("doc")),
            price : q.Select(["data","price"], q.Var("doc")),
            owner : q.Select(["data","owner"], q.Var("doc")),
            owner_name :
              q.Select(["data","name"],
              q.Get(q.Select(["data","owner"], q.Var("doc"))))
          }
        })
      )
    );
  }

listPlayers() {
    return this.client.query(
      q.Map(
        q.Paginate(q.Match(q.Index("players"))),
        (row) => q.Get(row)
      )
    );
  }