def get_grid_sizes(image_shape, base_grid_size):
    """utility function that compute the sizes of the grid system
    
    Arguments:
        image_shape {tuple} -- the shape of the image
        base_grid_size {int} -- the size of the cell in base grid
    
    Returns:
        list -- a list of the grid sizes
    """
    if base_grid_size == 32:
        return [int(image_shape[0] / x) for x in [32, 16, 8]]
    else:
        values = []
        for x in [base_grid_size, base_grid_size / 2, base_grid_size / 4]:
            # if image_shape[0] % x != 0:
            #     raise ValueError(
            #         f'the base grid size {base_grid_size} is not divisible per the image size'
            #     )
            values.append(int(image_shape[0] / x))

        return values