Highlights the current fold scope.

        :param block: Block that starts the current fold scope.

def _highlight_block(self, block):
        """
        Highlights the current fold scope.

        :param block: Block that starts the current fold scope.
        """
        scope = FoldScope(block)
        if (self._current_scope is None or
                self._current_scope.get_range() != scope.get_range()):
            self._current_scope = scope
            self._clear_scope_decos()
            # highlight current scope with darker or lighter color
            start, end = scope.get_range()
            if not TextBlockHelper.is_collapsed(block):
                self._decorate_block(start, end)