docs: async function prepareDataSource() {
      const orders = await fetchOrders()
      const ordersByShipCountry = orders.reduce((a, v) => {
          a[v.ShipCountry] = a[v.ShipCountry] || []
          a[v.ShipCountry].push(v)
          return a
      }, {})
  
      return Object.keys(ordersByShipCountry).map((country) => {
          const ordersInCountry = ordersByShipCountry[country]
  
          const accumulated = {}
  
          ordersInCountry.forEach((o) => {
              o.OrderDate = new Date(o.OrderDate);
              const key = o.OrderDate.getFullYear() + '/' + (o.OrderDate.getMonth() + 1);
              accumulated[key] = accumulated[key] || {
                  value: 0,
                  orderDate: o.OrderDate
              };
              accumulated[key].value++;
          });
  
          return {
              rows: ordersInCountry,
              country,
              accumulated
          }
  
      }).slice(0, 2)
  }