add docstring for depends

theano/gof/sched.py

@@ -12,6 +12,7 @@ def memodict(f):
 
 @memodict
 def depends((a, b)):
+    """ Returns True if a depends on b """
     return (any(bout in a.inputs for bout in b.outputs)
              or any(depends((ainp.owner, b)) for ainp in a.inputs
                                               if ainp.owner))