diff --git a/src/lineagetree/_io/_loaders.py b/src/lineagetree/_io/_loaders.py
index 3e8ff65..2b87710 100644
--- a/src/lineagetree/_io/_loaders.py
+++ b/src/lineagetree/_io/_loaders.py
@@ -106,10 +106,10 @@ def _load_meshdict_from_bmfmesh(bmfmesh, pos_multipliers, translation):
     translation = np.array(translation, dtype=float)
     vertices = vertices * pos_multipliers + translation
 
-    return { # could be a class
-        'vertices': vertices,
-        'faces': faces,
-        'center_mass': np.mean(vertices, axis=0),
+    return {  # could be a class
+        "vertices": vertices,
+        "faces": faces,
+        "center_mass": np.mean(vertices, axis=0),
     }
 
 
@@ -150,9 +150,11 @@ def read_from_bmf(
     for track in tracks:
         pred = None
         for t, mesh in track.meshes.items():
-            mesh = _load_meshdict_from_bmfmesh(mesh, pos_multipliers, translation)
+            mesh = _load_meshdict_from_bmfmesh(
+                mesh, pos_multipliers, translation
+            )
             pos[cell_id] = mesh["center_mass"]
-            
+
             if store_meshes:
                 lT_mesh[cell_id] = mesh
 
@@ -869,6 +871,8 @@ def read_from_mastodon(
     pos = dict(zip(nodes, spots[:, :3], strict=True))
     time = dict(zip(nodes, spots[:, 3], strict=True))
     predecessor = {}
+    labels, labels_name = {}, []
+
     for succ, pred in zip(links[:, 1], links[:, 0]):
         predecessor[int(succ)] = int(pred)