import alphashape
import geopandas as gpd

def concave_hull(coords, alpha):
    """
    Generate a concave hull (alphashape) from a set of coordinates.
    Parameters:
    - coords: List of (x, y) tuples representing the points.
    - alpha: Alpha parameter controlling the concavity. Smaller values result in a more detailed hull, while larger values produce a more convex hull.
    Returns:
    - A shapely geometry representing the concave hull.
    """
    hull = alphashape.alphashape(coords, alpha)
    return hull