Update the code to address the comment

src/pam/operations/snap.py

@@ -4,11 +4,11 @@
 
 import geopandas as gp
 import numpy as np
+from scipy.spatial import cKDTree
 
 from pam.core import Population
 from pam.read import read_matsim
 from pam.write import write_matsim
-from scipy.spatial import cKDTree
 
 
 def snap_facilities_to_network(
@@ -21,29 +21,19 @@ def snap_facilities_to_network(
         network (gp.GeoDataFrame): A network geometry shapefile.
         link_id_field (str, optional): The link ID field to use in the network shapefile. Defaults to "id".
     """
-    if network.geometry.geom_type[0] == 'Point':
+    if network.geometry.geom_type[0] == "Point":
         coordinates = np.array(list(zip(network.geometry.x, network.geometry.y)))
     else:
         coordinates = np.array(list(zip(network.geometry.centroid.x, network.geometry.centroid.y)))
 
     tree = cKDTree(coordinates)
     link_ids = network[link_id_field].values
 
-    activity_points = []
-    activities_info = []
     for _, _, person in population.people():
         for act in person.activities:
             point = act.location.loc
-            if not hasattr(point, 'x') or not hasattr(point, 'y'):
-                point = point.centroid
-            activity_points.append((point.x, point.y))
-            activities_info.append(act)
-
-    activity_points = np.array(activity_points)
-    distances, indices = tree.query(activity_points)
-
-    for act, index in zip(activities_info, indices):
-        act.location.link = link_ids[index]
+            distance, index = tree.query([(point.x, point.y)])
+            act.location.link = link_ids[index[0]]
 
 
 def run_facility_link_snapping(