code: def insert_before_extension(filename, content):
  	
  	parts = list(os.path.splitext(filename))
  	parts[1:1] = [content]
  	return ''.join(parts)
docs: Given a filename and some content, insert the content just before
  	the extension.
  
  	>>> insert_before_extension('pages.pdf', '-old')
  	'pages-old.pdf'