Inferring Yolo_v3.trt model in python

yes Morganh.I doublechecked my code and i changed the preprocessing as you suggest.But still i am getting negative values in bbox coordinates.can you please tell me why the bbox coordinates are come in negative index.
Here i attached the preprocessing steps

def _preprocess_yolo(self,img, letter_box=True):
“”"Preprocess an image before TRT YOLO inferencing.

# Args
    img: int8 numpy array of shape (img_h, img_w, 3)
    input_shape: a tuple of (H, W)
    letter_box: boolean, specifies whether to keep aspect ratio and
                create a "letterboxed" image for inference

# Returns
    preprocessed img: float32 numpy array of shape (3, H, W)
"""
input_shape = (self.model_h,self.model_w)
if letter_box:
    img_h, img_w, _ = img.shape
    new_h, new_w = input_shape[0], input_shape[1]
    offset_h, offset_w = 0, 0
    if (new_w / img_w) <= (new_h / img_h):
        new_h = int(img_h * new_w / img_w)
        offset_h = (input_shape[0] - new_h) // 2
    else:
        new_w = int(img_w * new_h / img_h)
        offset_w = (input_shape[1] - new_w) // 2
    resized = cv2.resize(img, (new_w, new_h))
    img = np.full((input_shape[0], input_shape[1], 3), 127, dtype=np.uint8)
    img[offset_h:(offset_h + new_h), offset_w:(offset_w + new_w), :] = resized
else:
    img = cv2.resize(img, (input_shape[1], input_shape[0]))

img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
img = img.astype(np.float32)
img = img.transpose((2, 0, 1))
img = preprocess_input(img)
return img.ravel()