from shapely.geometry import Polygon, MultiPolygon, shape, Point
import geopandas as gp
def convert_3D_2D(geometry):
    '''
    Takes a GeoSeries of 3D Multi/Polygons (has_z) and returns a list of 2D Multi/Polygons
    '''
    new_geo = []
    for p in geometry:
        if p.has_z:
            if p.geom_type == 'Polygon':
                lines = [xy[:2] for xy in list(p.exterior.coords)]
                new_p = Polygon(lines)
                new_geo.append(new_p)
            elif p.geom_type == 'MultiPolygon':
                new_multi_p = []
                for ap in p:
                    lines = [xy[:2] for xy in list(ap.exterior.coords)]
                    new_p = Polygon(lines)
                    new_multi_p.append(new_p)
                new_geo.append(MultiPolygon(new_multi_p))
    return new_geo

import geopandas as gpd
from shapely import wkb

_drop_z = lambda geom: wkb.loads(wkb.dumps(geom, output_dimension=2))
df.geometry = df.geometry.transform(_drop_z)