[examples] clean up imports

examples/tutorial/basic_shapes.py

@@ -1,11 +1,9 @@
-from collections.abc import Sequence
 
 import numpy
 from numpy import pi
 
 from masque import (
-    layer_t, Pattern, Label, Port,
-    Circle, Arc, Polygon,
+    layer_t, Pattern, Circle, Arc, Polygon,
     )
 import masque.file.gdsii