def compare_polys(poly_a, poly_b):
    """Compares two polygons via IoU.

    Input:
        poly_a: A Shapely polygon.
        poly_b: Another Shapely polygon.

    Returns:
        The IoU between these two polygons.
    """
    intersection = poly_a.intersection(poly_b).area
    union = poly_a.union(poly_b).area
    jaccard = intersection/union
    return jaccard