make doc appear

doc/library/tensor/index.txt

@@ -25,5 +25,6 @@ They are grouped into the following sections:
     utils
     extra_ops
     io
+    opt
     slinalg
     nlinalg

theano/tensor/opt.py

@@ -4074,11 +4074,11 @@ class Canonizer(gof.LocalOptimizer):
 
     Examples
     --------
-      T = theano.tensor
-      add_canonizer = Canonizer(T.add, T.sub, T.neg,
-                                lambda n, d: sum(n) - sum(d))
-      mul_canonizer = Canonizer(T.mul, T.true_div, T.inv,
-                                lambda n, d: prod(n) / prod(d))
+    >>> T = theano.tensor
+    >>> add_canonizer = Canonizer(T.add, T.sub, T.neg,
+                                  lambda n, d: sum(n) - sum(d))
+    >>> mul_canonizer = Canonizer(T.mul, T.true_div, T.inv,
+                                  lambda n, d: prod(n) / prod(d))
 
     Examples of optimizations mul_canonizer can perform:
       x / x -> 1