What was the change in net revenue from Sanmina from 2018 to 2019?
{"Contract manufacturers and consignment warehouses:        -- Flextronics Technology": {"2019": 21.8, "2018": 14.0, "2017": 10.4}, "Contract manufacturers and consignment warehouses:        -- Sanmina": {"2019": 17.7, "2018": 16.0, "2017": 20.4}, "Distributors:        -- Avnet Logistics": {"2019": 31.3, "2018": 35.3, "2017": 25.5}, "Distributors:        -- Nexcomm ": {"2019": 14.8, "2018": 16.1, "2017": 19.7}}
revenue_2019 = df["Contract manufacturers and consignment warehouses:        -- Sanmina"]["2019"]
revenue_2018 = df["Contract manufacturers and consignment warehouses:        -- Sanmina"]["2018"]
answer = revenue_2019 - revenue_2018