# File lib/symetrie_com/acts_as_better_nested_set.rb, line 505
        def previous_siblings(scope = {})
          self.class.find_in_nested_set(:all, 
            { :conditions => ["#{scope_condition} AND #{sibling_condition} AND #{self.class.table_name}.id != ? AND #{prefixed_right_col_name} < ?", self.id, self[left_col_name]], :order => "#{prefixed_left_col_name} DESC" }, scope)
        end