code: def get_input_files(dirname, *ext):
      
      filelist = [f for f in os.listdir(dirname) if
                  os.path.splitext(f)[-1] in ext]
      return [os.path.join(dirname, f) for f in filelist]
docs: Returns files in passed directory, filtered by extension.
  
      - dirname - path to input directory
      - *ext - list of arguments describing permitted file extensions