user: Question: What company constructed the vehicle when the driver shows as Not held?
Columns: ['Year', 'Driver', 'Constructor', 'Category', 'Location', 'Report']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['1958', 'Stirling Moss', 'Vanwall', 'Formula One', 'Ain-Diab', 'Report']
SQL:

assistant: SELECT "Constructor" FROM "Table" WHERE "Driver" = 'Not held';