identification of the checkboxes in opencv in a form

enter image description hereI have been trying to identify the check-boxes in a form. I am able to find the contours of the check-boxes and extract them. I want them to have an order such that they move in a left to right and top to bottom fashion.

I cropped the contours that matched the check-boxes in the form. I want to identify the check-boxes with the key associated.

This sort the contours

def sort_contours(cnts, method="left-to-right"):
    # initialize the reverse flag and sort index
    reverse = False
    i = 0
    # handle if we need to sort in reverse
    if method == "right-to-left" or method == "bottom-to-top":
        reverse = True
    # handle if we are sorting against the y-coordinate rather than
    # the x-coordinate of the bounding box
    if method == "top-to-bottom" or method == "bottom-to-top":
        i = 1
    # construct the list of bounding boxes and sort them from top to
    # bottom
    boundingBoxes = [cv2.boundingRect(c) for c in cnts]
    (cnts, boundingBoxes) = zip(*sorted(zip(cnts, boundingBoxes),
                                        key=lambda b: b[1][i], reverse=reverse))
    # return the list of sorted contours
    return cnts

THIS GIVES THE CONTOURS IN THE IMAGE

[for c in sorted_cnts :
    peri = cv2.arcLength(c, True)
    approx = cv2.approxPolyDP(c, 0.035 * peri, True)

    (x, y, w, h) = cv2.boundingRect(approx)
    aspect_ratio = w / float(h)
    area = cv2.contourArea(c) 
    if area < threshold_max_area and area > threshold_min_area and (aspect_ratio >= 0.9 and aspect_ratio <= 1):
        cv2.drawContours(original_image,\[c\], 0, (0,255,0), 3)

        x,y,w,h = cv2.boundingRect(c)
        roi=original_image\[y:y+h,x:x+w\]
        cv2.imwrite(str(idx) + '.jpg', roi)
        print(x,y,w,h)
        checkbox_contours.append(c)][1]

I am trying to find the key along with checkbox and its status