code: def to_filename(s):
      
      s = re.sub(r'(?u)[^-\w. ]', '', s)
      s = s.strip().replace(' ', '_')
      return s
docs: Based on `django/utils/text.py <https://github.com/django/django/blob/master/django/utils/text.py>`_.
      Return the given string converted to a string that can be used for a clean filename.
      Specifically, leading and trailing spaces are removed; other spaces are converted to underscores, and anything that is not a unicode alphanumeric, dash, underscore, or dot, is removed.
  
      EXAMPLE::
  
          >>> to_filename("%  A d\sbla'{-+\)(ç? ")
          'A_dsbla-ç'