def adjust_bounding_box(bbox):
    """Adjust the bounding box as specified by user.
    Returns the adjusted bounding box.

    - bbox: Bounding box computed from the canvas drawings.
    It must be a four-tuple of numbers.
    """
    for i in range(0, 4):
        if i in bounding_box:
            bbox[i] = bounding_box[i]
        else:
            bbox[i] += delta_bounding_box[i]
    return bbox
Adjust the bounding box as specified by user.
    Returns the adjusted bounding box.

    - bbox: Bounding box computed from the canvas drawings.
    It must be a four-tuple of numbers.