chore:try3 fixing flake8 errors

src/meanvariancefunction.py

@@ -26,6 +26,7 @@ def mean_variance(filepath: str, output_dir: str = os.getcwd()+'/') -> str:
         ValueError: If there are no files in directory
 
     """
+
     # Open each file in the input directory, raises error if no file is found
     files = [file for file in glob(filepath)]