What was the change in Pro forma revenues between 2017 and 2018?
{"Pro forma revenues (3)": {"2018 (1)": 1217655.0, "2017 (2)": 1060777.0}, "Pro forma net income from continuing operations available to common stockholders (3)": {"2018 (1)": 51975.0, "2017 (2)": 226086.0}, "Pro forma earnings per common share - basic (3)": {"2018 (1)": 0.98, "2017 (2)": 4.86}, "Pro forma earnings per common share - diluted (3)": {"2018 (1)": 0.89, "2017 (2)": 4.08}, "Pro forma common shares - basic": {"2018 (1)": 52798.0, "2017 (2)": 46552.0}, "Pro forma common shares - diluted": {"2018 (1)": 58640.0, "2017 (2)": 55389.0}}
pro_forma_revenues_3_2018_1 = df["Pro forma revenues (3)"]["2018 (1)"]
pro_forma_revenues_3_2017_2 = df["Pro forma revenues (3)"]["2017 (2)"]
answer = pro_forma_revenues_3_2018_1 - pro_forma_revenues_3_2017_2