What was the change in the Foreign exchange contracts between 2017 and 2019?
{"Foreign currency translation adjustment": {"Financial Statement Line Item": "Operating income", "2019": "$\u2014", "2018": "$\u2014", "2017": 5947}, "Realized losses (gains) on derivative instruments:(3) -- Foreign exchange contracts": {"Financial Statement Line Item": "Cost of revenue", "2019": 21982, "2018": -9379, "2017": 4799}, "Realized losses (gains) on derivative instruments:(3) -- Interest rate contracts": {"Financial Statement Line Item": "Interest expense", "2019": -1723, "2018": -13697, "2017": 3950}, "Realized losses (gains) on derivative instruments:(3) -- Actuarial loss": {"Financial Statement Line Item": -1, "2019": 741, "2018": 1127, "2017": 1929}, "Realized losses (gains) on derivative instruments:(3) -- Prior service credit": {"Financial Statement Line Item": -1, "2019": -44, "2018": -88, "2017": -138}, "Realized losses (gains) on derivative instruments:(3) -- Available for sale securities": {"Financial Statement Line Item": -2, "2019": 33333, "2018": "\u2014", "2017": 10139}, "Realized losses (gains) on derivative instruments:(3) -- Total amounts reclassified from AOCI(4)": {"Financial Statement Line Item": "", "2019": 54289, "2018": -22037, "2017": 26626}}
fx_2019 = df["Realized losses (gains) on derivative instruments:(3) -- Foreign exchange contracts"]["2019"]
fx_2017 = df["Realized losses (gains) on derivative instruments:(3) -- Foreign exchange contracts"]["2017"]
answer = fx_2019 - fx_2017