def filter_polygons(state, header):
    """
    Removes any non-polygon sources from the state file.

    We are only interested in parsing parcel data, which is
    marked as Polygon in the state file.
    """
    filtered_state = []

    for source in state:
        if 'Polygon' in source[header.index('geometry type')]:
            filtered_state.append(source)

    return filtered_state