replaced Attribute error catching with call to new get_parents method

theano/gof/destroyhandler.py

@@ -125,13 +125,14 @@ def _contains_cycle(inputs, outputs, orderings):
                 assert not orderings.get(cur_var_or_node, False)
                 expand_l = []
             else:
-                try:
-                    if cur_var_or_node.owner:
-                        expand_l = [cur_var_or_node.owner]
-                    else:
-                        expand_l = []
-                except AttributeError:
-                    expand_l = list(cur_var_or_node.inputs)
+                expand_l = cur_var_or_node.get_parents()
+                #try:
+                #    if cur_var_or_node.owner:
+                #        expand_l = [cur_var_or_node.owner]
+                #    else:
+                #        expand_l = []
+                #except AttributeError:
+                #    expand_l = list(cur_var_or_node.inputs)
                 expand_l.extend(orderings.get(cur_var_or_node, []))
 
             if expand_l:

theano/gof/graph.py

@@ -202,6 +202,9 @@ class Apply(utils.object2):
             new_node.inputs = new_inputs
         return new_node
 
+    def get_parents(self):
+        return list( self.inputs )
+
     #convenience properties
     nin = property(lambda self: len(self.inputs), doc='same as len(self.inputs)')
     """property: Number of inputs"""
@@ -364,6 +367,11 @@ class Variable(utils.object2):
         raise NotImplementedError('Subclasses of Variable must provide __ge__',
                                   self.__class__.__name__)
 
+    def get_parents(self):
+        if self.owner is not None:
+            return [ self.owner ]
+        return [ ]
+
     def env_getter(self):
         warnings.warn("Variable.env is deprecated, it has been renamed 'fgraph'",
                 stacklevel=2)