from typing import List


def keys() -> List[str]:
    """Particle attribute names

    Returns:
        List[str]: attribute names
    """
    return [
        "perim",
        "hull_area",
        "convex_perim",
        "blur",
        "contours",
        "contrast",
        "cnt_area",
        "circularity",
        "solidity",
        "complexity",
        "equiv_d",
        "phi",
        "extreme_points",
        "filled_circular_area_ratio",
        "roundness",
        "perim_area_ratio",
    ]