How many percent did the revenue increase from the year 2017 to 2018?
{"Subscription service revenue": {"2019": 849267, "2018": 681138, "2017": 489274}, "Subscription software revenue": {"2019": 25739, "2018": 23262, "2017": 17081}, "Hardware and services": {"2019": 13184, "2018": 12594, "2017": 13326}, "Total revenue": {"2019": 888190, "2018": 716994, "2017": 519681}}
total_revenue_2018 = df["Total revenue"]["2018"]
total_revenue_2017 = df["Total revenue"]["2017"]
answer = (total_revenue_2018 - total_revenue_2017) / total_revenue_2017 * 100.0