docs: def set_indent(TokenClass, implicit=False):
      """Set the previously saved indentation level."""
      def callback(lexer, match, context):
          text = match.group()
          if context.indent < context.next_indent:
              context.indent_stack.append(context.indent)
              context.indent = context.next_indent
          if not implicit:
              context.next_indent += len(text)
          yield match.start(), TokenClass, text
          context.pos = match.end()
      return callback