import json
from urllib import request

data = json.dumps({
    "frame_id": 26, # Need a valid frame_id! Let's get one from the db
    "engine": "sam3",
    "threshold": 0.35,
    "iou_threshold": 0.8,
    "min_box_frac": 0.0,
    "target_class_names": ["sack"]
}).encode('utf-8')

req = request.Request('http://localhost:8000/api/batches/5/preview', data=data, headers={'Content-Type': 'application/json'})
try:
    with request.urlopen(req) as response:
        print(response.read().decode('utf-8'))
except Exception as e:
    print("Error:", getattr(e, 'read', lambda: str(e))())