added method to_dios

dios/dios.py

@@ -778,6 +778,13 @@ class DictOfSeries(_DiosBase):
         """ Alias, see ``notna()``. """
         return self.notna(drop_empty=drop_empty)
 
+    def to_dios(self):
+        """
+        A dummy to allow unconditional to_dios calls
+        on pd.DataFrame, pd.Series and dios.DictOfSeries
+        """
+        return self
+
     # ----------------------------------------------------------------------
     # Rendering Methods