code: def jcrop_css(css_url=None):
          
          if css_url is None:
              if current_app.config['AVATARS_SERVE_LOCAL']:
                  css_url = url_for('avatars.static', filename='jcrop/css/jquery.Jcrop.min.css')
              else:
                  css_url = 'https://cdn.jsdelivr.net/npm/jcrop-0.9.12@0.9.12/css/jquery.Jcrop.min.css'
          return Markup('<link rel="stylesheet" href="%s">' % css_url)
docs: Load jcrop css file.
  
          :param css_url: The custom CSS URL.