Make NodeFinder hashable.

theano/gof/toolbox.py

@@ -248,10 +248,11 @@ class ReplaceValidate(History, Validator):
                 raise ReplacementDidntRemovedError()
 
 
-class NodeFinder(dict, Bookkeeper):
+class NodeFinder(Bookkeeper):
 
     def __init__(self):
         self.fgraph = None
+        self.d = {}
 
     def on_attach(self, fgraph):
         if self.fgraph is not None:
@@ -273,7 +274,7 @@ class NodeFinder(dict, Bookkeeper):
 
     def on_import(self, fgraph, node, reason):
         try:
-            self.setdefault(node.op, []).append(node)
+            self.d.setdefault(node.op, []).append(node)
         except TypeError:  # node.op is unhashable
             return
         except Exception, e:
@@ -286,16 +287,16 @@ class NodeFinder(dict, Bookkeeper):
 
     def on_prune(self, fgraph, node, reason):
         try:
-            nodes = self[node.op]
+            nodes = self.d[node.op]
         except TypeError:  # node.op is unhashable
             return
         nodes.remove(node)
         if not nodes:
-            del self[node.op]
+            del self.d[node.op]
 
     def query(self, fgraph, op):
         try:
-            all = self.get(op, [])
+            all = self.d.get(op, [])
         except TypeError:
             raise TypeError("%s in unhashable and cannot be queried by the"
                             " optimizer" % op)