add sts for bos (#736)

visualdl/io/bfile.py

@@ -218,9 +218,10 @@ class BosFileSystem(object):
             raise KeyError('${BOS_SK} is not found.')
         self.max_contents_count = int(os.getenv('BOS_CACHE_COUNT', 1))
         self.max_contents_time = int(os.getenv('BOS_CACHE_TIME', 1))
+        bos_sts = os.getenv("BOS_STS")
         self.config = BceClientConfiguration(
             credentials=BceCredentials(access_key_id, secret_access_key),
-            endpoint=bos_host)
+            endpoint=bos_host, security_token=bos_sts)
 
     def isfile(self, filename):
         return exists(filename)