user: Question: Which Object type has an NGC number of 2171?
Columns: ['NGC number', 'Object type', 'Constellation', 'Right ascension ( J2000 )', 'Declination ( J2000 )']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [2129.0, 'Open cluster', 'Gemini', '06h01m06s', '°19′20″']
SQL:

assistant: SELECT "Object type" FROM "Table" WHERE "NGC number" = 2171.0;