+class Layer:
+ """ A single layer of actors. """
+
+ def __init__(self, name):
+ self.name = name
+ self.actors = []
+
+ def __iter__(self):
+ return iter(self.actors)
+
+ def add(self, actor):
+ self.actors.append(actor)
+ return actor
+
+ def remove(self, actor):
+ self.actors.remove(actor)
+ return actor
+
+