Simplify lazy loader

Signed-off-by: Bram Stoeller <[email protected]>

src/power_grid_model_io/data_stores/excel_file_store.py

@@ -78,7 +78,7 @@ def sheet_loader():
  excel_file = pd.ExcelFile(path)
  for sheet_name in excel_file.sheet_names:
  loader = lazy_sheet_loader(excel_file, sheet_name)
- if name:
+ if name != "": # If the Excel file is not the main file, prefix the sheet name with the file name
  sheet_name = f"{name}.{sheet_name}"
  if sheet_name in data:
  raise ValueError(f"Duplicate sheet name '{sheet_name}'")