What is the total number of subscribers in 2019?
{"Consumer / SMB Fiber Revenue (in millions):": {"2018": 87.2, "2019": 42.3}, "Subscribers (in thousands): -- High-speed internet": {"2018": 68.2, "2019": 65.9}, "Subscribers (in thousands): -- Video": {"2018": 42.7, "2019": 48.8}, "Subscribers (in thousands): -- Voice": {"2018": 30.0, "2019": 30.3}}
total_subscribers = df["Subscribers (in thousands): -- High-speed internet"]["2018"] + df["Subscribers (in thousands): -- Video"]["2018"] + df["Subscribers (in thousands): -- Voice"]["2018"]