update io.py annotations and codes

Author: seiriosPlus

python/paddle/fluid/io.py

@@ -483,11 +483,11 @@ def save_checkpoint(executor,
     :param main_program
     :param max_num_checkpoints
     """
-    if checkpoint_dir is None:
-        raise ValueError("The values of 'checkpoint_dir' should not be None")
+    if checkpoint_dir.strip() is None:
+        raise ValueError("'checkpoint_dir' should not be None")
 
-    if trainer_args and not isinstance(trainer_args, dict):
-        raise TypeError("The type of 'trainer_args' should be dict")
+    if trainer_args:
+        assert isinstance(trainer_args, dict)
 
     if not os.path.isdir(checkpoint_dir):
         os.makedirs(checkpoint_dir)
@@ -514,11 +514,11 @@ def load_checkpoint(executor, checkpoint_dir, serial, main_program):
     :param main_program
     """
 
-    if checkpoint_dir is None:
-        raise ValueError("The values of 'checkpoint_dir' should not be None")
+    if checkpoint_dir.strip() is None:
+        raise ValueError("'checkpoint_dir' should not be None")
 
     if serial is None or serial < 0:
-        raise ValueError("The values of 'serial' should not be None or <0 ")
+        raise ValueError("'serial' should not be None or <0 ")
 
     if main_program is None:
         raise ValueError('main_program should not be None.')
@@ -536,8 +536,8 @@ def clean_checkpoint(checkpoint_dir, delete_dir=False):
     :param delete_dir
     """
 
-    if checkpoint_dir is None:
-        raise ValueError("The values of 'checkpoint_dir' should not be None")
+    if checkpoint_dir.strip() is None:
+        raise ValueError("'checkpoint_dir' should not be None")
     _lru_delete(checkpoint_dir, max_num_checkpoints=0)
 
     if delete_dir and not os.listdir(checkpoint_dir):
@@ -590,8 +590,8 @@ def save_persist_vars_without_grad(executor, dirname, program):
 
 
 def save_trainer_args(dirname, trainer_id, trainer_args):
-    if not isinstance(trainer_args, dict):
-        raise TypeError("The type of 'trainer_args' should be dict")
+    assert isinstance(trainer_args, dict)
+
     cur_dir = _get_trainer_dir(dirname, trainer_id)
 
     for name, value in trainer_args.iteritems():
@@ -602,12 +602,11 @@ def save_trainer_args(dirname, trainer_id, trainer_args):
 
 
 def load_trainer_args(checkpoint_dir, serial, trainer_id, trainer_args):
+    assert isinstance(trainer_args, list)
+
     cur_dir = _get_serial_dir(checkpoint_dir, serial)
     cur_dir = _get_trainer_dir(cur_dir, trainer_id)
 
-    if not isinstance(trainer_args, list):
-        raise TypeError("The type of 'trainer_args' should be list")
-
     ret_values = []
 
     for arg in trainer_args: