diff --git a/src/icartt/dataset.py b/src/icartt/dataset.py
index 86065c4bad864aa067f4eed0cdbf187bf1ff2eb6..5741810de56d003b360e48569554897b5c8a192c 100644
--- a/src/icartt/dataset.py
+++ b/src/icartt/dataset.py
@@ -125,7 +125,7 @@ class DataStore2110(collections.UserDict):
         self.add(**newdata)
 
     def addBulkDep(self, ivar, raw):
-        nlines, nvars = raw.shape
+        nlines, nvars = raw.shape # nvars not used
         self._addDeplines(ivar, raw, nlines)
 
     def _addDeplines(self, ivar, raw, n):
@@ -491,6 +491,10 @@ class Dataset:
             self.format = Formats(int(dmp[1]))
         except:
             raise ValueError("ICARTT format {:d} not implemented".format(dmp[1]))
+            # TODO except clause could be re-written like
+            # except ValueError as ve:
+            #     raise ValueError(f"ICARTT format {dmp[1]:d} not implemented") from ve
+            # to show the error trace
 
         if len(dmp) > 2:
             self.version = dmp[2]