nodes: 0, module; 1, function_definition; 2, function_name:sortable_title; 3, parameters; 4, block; 5, identifier:instance; 6, expression_statement; 7, expression_statement; 8, if_statement; 9, return_statement; 10, comment:"""Uses the default Plone sortable_text index lower-case
      """; 11, assignment; 12, call; 13, block; 14, call; 15, identifier:title; 16, call; 17, identifier:safe_callable; 18, argument_list; 19, expression_statement; 20, attribute; 21, argument_list; 22, identifier:plone_sortable_title; 23, argument_list; 24, identifier:title; 25, assignment; 26, identifier:title; 27, identifier:lower; 28, identifier:instance; 29, identifier:title; 30, call; 31, identifier:title; 32, argument_list
code: def sortable_title(instance):
      """Uses the default Plone sortable_text index lower-case
      """
      title = plone_sortable_title(instance)
      if safe_callable(title):
          title = title()
      return title.lower()