Squashed 'dagflow/' changes from 03ae5dc..9c27501

9c27501 feat: load_variables, enable loading the files
REVERT: 03ae5dc feat: load_variables, enable loading the files

git-subtree-dir: dagflow
git-subtree-split: 9c275017a5ed555427ec0dee639e32e3d6aa5a49

dagflow/bundles/load_variables.py

@@ -69,7 +69,7 @@ IsVarsCfgDict = Schema({
     })
 IsProperVarsCfgDict = And(IsVarsCfgDict, ParsCfgHasProperFormat())
 IsLoadableDict = And(
-            {'load': 'str'},
+            {'load': str},
             Use(LoadFileWithExt(yaml=LoadYaml, key='load'))
         )
 IsProperVarsCfg = Or(IsProperVarsCfgDict, And(IsLoadableDict, IsProperVarsCfgDict))