What is the change in the gross interest expense in 2019 from 2018?
{"Interest expense: -- Gross interest expense": {"2019": 2093, "2018": 2230, "2017": 1559}, "Interest expense: -- Capitalized interest": {"2019": -72, "2018": -53, "2017": -78}, "Interest expense: -- Total interest expense": {"2019": 2021, "2018": 2177, "2017": 1481}}
gross_interest_expense_2019 = df["Interest expense: -- Gross interest expense"]["2019"]
gross_interest_expense_2018 = df["Interest expense: -- Gross interest expense"]["2018"]
answer = gross_interest_expense_2019 - gross_interest_expense_2018