How many pairs of object samples in image no.1 have the relation of "parked on"?
pairs of object samples refers to OBJ1_SAMPLE_ID and OBJ2_SAMPLE_ID; image no.1 refers to IMG_ID = 1; relation of "parked on" refers to PRED_CLASS = 'parked on'
SELECT SUM(CASE WHEN T1.PRED_CLASS = 'parked on' THEN 1 ELSE 0 END) FROM PRED_CLASSES AS T1 INNER JOIN IMG_REL AS T2 ON T1.PRED_CLASS_ID = T2.PRED_CLASS_ID WHERE T2.IMG_ID = 1 AND T2.OBJ1_SAMPLE_ID != OBJ2_SAMPLE_ID