move flatten to the utils module.

theano/gof/compiledir.py

@@ -11,6 +11,7 @@ import numpy
 
 import theano
 from theano.configparser import config, AddConfigVar, ConfigParam, StrParam
+from theano.gof.utils import flatten
 
 compiledir_format_dict = {"platform": platform.platform(),
                           "processor": platform.processor(),
@@ -109,16 +110,6 @@ AddConfigVar('compiledir',
             allow_override=False))
 
 
-def flatten(a):
-    if isinstance(a, (tuple, list, set)):
-        l = []
-        for item in a:
-            l.extend(flatten(item))
-        return l
-    else:
-        return [a]
-
-
 def cleanup():
     """
     Delete keys in old format from the compiledir.

theano/gof/utils.py

@@ -332,3 +332,12 @@ def type_guard(type1):
         return new_f
     return wrap
 
+
+def flatten(a):
+    if isinstance(a, (tuple, list, set)):
+        l = []
+        for item in a:
+            l.extend(flatten(item))
+        return l
+    else:
+        return [a]