overwrite previous changes to DataConverter

src/graphnet/data/dataconverter.py

@@ -1,4 +1,5 @@
 """Contains `DataConverter`."""
+
 from typing import List, Union, OrderedDict, Dict, Tuple, Any, Optional, Type
 from abc import ABC
 
@@ -260,8 +261,8 @@ def _request_event_nos(self, n_ids: int) -> List[int]:
                 event_nos = np.arange(start_idx, start_idx + n_ids, 1).tolist()
                 global_index.value += n_ids  # type: ignore[name-defined]
         else:
-            starting_index = self._index
-            event_nos = np.arange(starting_index, starting_index + n_ids, 1).tolist()
+            start_idx = self._index
+            event_nos = np.arange(start_idx, start_idx + n_ids, 1).tolist()
             self._index += n_ids
 
         return event_nos
@@ -316,7 +317,9 @@ def _update_shared_variables(
             self._output_files.extend(list(sorted(output_files[:])))
 
     @final
-    def merge_files(self, files: Optional[List[str]] = None, **kwargs: Any) -> None:
+    def merge_files(
+        self, files: Optional[Union[List[str], str]] = None, **kwargs: Any
+    ) -> None:
         """Merge converted files.
 
             `DataConverter` will call the `.merge_files` method in the
@@ -332,7 +335,9 @@ def merge_files(self, files: Optional[List[str]] = None, **kwargs: Any) -> None:
         elif files is not None:
             # Proceed to merge specified by user.
             if isinstance(files, str):
-                files = [files]  # Cast to list if user forgot
+                # We shouldn't merge a single file?
+                self.info(f"Got just a single file {files}. Merging skipped.")
+                return
             files_to_merge = files
         else:
             # Raise error