Please list the IDs of all the trains with at least one car in a non-regular shape.
non-regular shape refers to shape in ('elipse', 'bucket')
SELECT train_id FROM cars WHERE shape IN ('elipse', 'bucket') GROUP BY train_id
database name:db_id trains
cars table cars Cols: id dtype integer, train id dtype integer, position dtype integer, shape dtype text, length dtype text, sides dtype text, roof dtype text, wheels dtype integer, load_shape dtype text, load number dtype integer, 
trains table trains Cols: id dtype integer, direction dtype text, 
