fix errors

Author: JiayiFeng

python/paddle/fluid/backward.py

@@ -489,10 +489,10 @@ def append_backward(loss, parameter_list=None, no_grad_set=None,
     Examples:
         .. code-block:: python
 
-        # network configuration code
-        # ...
-        avg_loss = fluid.layers.mean(loss)
-        param_grad_list = fluid.backward.append_backward(loss=avg_loss)
+            # network configuration code
+            # ...
+            avg_loss = fluid.layers.mean(loss)
+            param_grad_list = fluid.backward.append_backward(loss=avg_loss)
     """
     assert isinstance(loss, framework.Variable)
 

python/paddle/fluid/io.py

@@ -886,8 +886,8 @@ def load_checkpoint(executor, checkpoint_dir, serial, main_program):
     `checkpoint_dir` directory.
 
     In the training precess, we generally save a checkpoint in each
-    iteration. So there are more than one checkpoint in the
-    `checkpoint_dir`(each checkpoint has its own sub folder), use
+    iteration. So there are more than one checkpoint in the 
+    `checkpoint_dir` (each checkpoint has its own sub folder), use 
     `serial` to specify which serial of checkpoint you would like to
     load.