Add correct docstring

Co-authored-by: Peter Hill <[email protected]>

src/sdf_xarray/__init__.py

@@ -231,6 +231,7 @@ def guess_can_open(self, filename_or_obj):
 
 
 class SDFPreprocess:
+    """Preprocess SDF files for xarray ensuring matching job ids and sets time dimension"""
     def __init__(self):
         self.job_id: int | None = None