user: Question: What is the wheel arrangement for the model that was retired in 1955?
Columns: ['Class', 'Wheel arrangement', 'Fleet number(s)', 'Manufacturer', 'Serial numbers', 'Year made', 'Quantity made', 'Quantity preserved', 'Year(s) retired']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['4-8-4 — ooOOOOoo — Northern', '4-8-4 — ooOOOOoo — Northern', '4-8-4 — ooOOOOoo — Northern', '4-8-4 — ooOOOOoo — Northern', '4-8-4 — ooOOOOoo — Northern', '4-8-4 — ooOOOOoo — Northern', '4-8-4 — ooOOOOoo — Northern', '4-8-4 — ooOOOOoo — Northern', '4-8-4 — ooOOOOoo — Northern']
SQL:

assistant: SELECT "Wheel arrangement" FROM "Table" WHERE "Year(s) retired" = '1955';