code: def _thumbnail_div(target_dir, src_dir, fname, snippet, is_backref=False,
                     check=True):
      
      thumb, _ = _find_image_ext(
          os.path.join(target_dir, 'images', 'thumb',
                       'sphx_glr_%s_thumb.png' % fname[:-3]))
      if check and not os.path.isfile(thumb):
          # This means we have done something wrong in creating our thumbnail!
          raise RuntimeError('Could not find internal sphinx-gallery thumbnail '
                             'file:\n%s' % (thumb,))
      thumb = os.path.relpath(thumb, src_dir)
      full_dir = os.path.relpath(target_dir, src_dir)
  
      # Inside rst files forward slash defines paths
      thumb = thumb.replace(os.sep, "/")
  
      ref_name = os.path.join(full_dir, fname).replace(os.path.sep, '_')
  
      template = BACKREF_THUMBNAIL_TEMPLATE if is_backref else THUMBNAIL_TEMPLATE
      return template.format(snippet=escape(snippet),
                             thumbnail=thumb, ref_name=ref_name)
docs: Generates RST to place a thumbnail in a gallery