user: Question: What is the average year for Maserati Straight-4 Engines?
Columns: ['Year', 'Entrant', 'Chassis', 'Engine', 'Points']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [1953.0, 'Equipe Gordini', 'Gordini Type 16', 'Gordini Straight-6', 0.0]
SQL:

assistant: SELECT AVG("Year") FROM "Table" WHERE "Engine" = 'Maserati Straight-4';