Fixed double shift implementation. Added implicit renaming

src/workflow/DefaultDataPresenter.py

@@ -45,7 +45,7 @@ class DefaultDataPresenter(DataPresenter):
             mappings[key] = key
         elif key.endswith(".*"):
           # all fields in a sub-object
-          if value != "*":
+          if value != "*" and value != "":
             raise ValueError("Only '*' is accepted when renaming wildcard.")
           obj_path = key[:-2]
           sub_obj = data.get(obj_path)
@@ -86,6 +86,8 @@ class DefaultDataPresenter(DataPresenter):
     for mapping in self._split_definitions:
       if "=" in mapping:
         key, value = [s.strip() for s in mapping.split('=', 1)]
+        if not value:
+          value = key.split(".")[-1]
         mappings[key] = value
       else:
         mappings[mapping] = mapping