Fix type documentation for readChannels

Change return type from DataTypeModel to Set[str].

sohstationviewer/controller/processing.py

@@ -60,13 +60,13 @@ def loadData(dataType: str, tracking_box: QTextBrowser, listOfDir: List[str],
 
 
 def readChannels(tracking_box: QTextBrowser, listOfDir: List[str]
-                 ) -> DataTypeModel:
+                 ) -> Set[str]:
     """
     Scan available channels (to be used in channel preferences dialog). Since
         channels for RT130 is hard code, this function won't be applied for it.
     :param tracking_box: QTextBrowser - widget to display tracking info
     :param listOfDir: [str,] - list of directories selected by users
-    :return dataObject: DataTypeModel - object that keep the data read from
+    :return dataObject: {str,} - object that keep the data read from
         listOfDir
     """
     dataObject = None