Add doc/ref about the new Type method.

theano/gof/type.py

@@ -343,6 +343,15 @@ class PureType(object):
         """
         return self.values_eq(a, b)
 
+#    def get_shape_info(self, obj):
+        """
+        Optional function. See TensorType().get_shape_info for definition
+        """
+
+#    def get_size(self, shape_info):
+        """
+        Optional function. See TensorType().get_size for definition
+        """
 
 _nothing = """
        """