code: def is_partial(self, filepath):
          
          path, filename = os.path.split(filepath)
          return filename.startswith('_')
docs: Check if file is a Sass partial source (see
          `Sass partials Reference`_).
  
          Args:
              filepath (str): A file path. Can be absolute, relative or just a
              filename.
  
          Returns:
              bool: True if file is a partial source, else False.