def from_postgis_polygon(polygon: str) -> list[tuple[float, float]]:
    boundary = polygon.lower().removeprefix('polygon((').removesuffix('))').split(',')
    xys = []
    for pt in boundary:
        xy = pt.split(' ')
        xys.append((float(xy[0]), float(xy[1])))
    return xys


def to_postgis_polygon(boundary: list[tuple[float, float]]) -> str:
    polygon = ''
    for pt in boundary:
        polygon += f'{pt[0]} {pt[1]},'
    return f'polygon(({polygon[:-1]}))'