def flatten_rule(rule)
      while rule.children.size == 1 && rule.children.first.is_a?(Tree::RuleNode)
        child = rule.children.first

        if first_simple_sel(child).is_a?(Sass::Selector::Parent)
          rule.parsed_rules = child.parsed_rules.resolve_parent_refs(rule.parsed_rules)
        else
          rule.parsed_rules = make_seq(*(first_seq(rule).members + first_seq(child).members))
        end

        rule.children = child.children
      end

      flatten_rules(rule)
    end
def flatten_rule(rule)
      while rule.children.size == 1 && rule.children.first.is_a?(Tree::RuleNode)
        child = rule.children.first

        if first_simple_sel(child).is_a?(Sass::Selector::Parent)
          rule.parsed_rules = child.parsed_rules.resolve_parent_refs(rule.parsed_rules)
        else
          rule.parsed_rules = make_seq(*(first_seq(rule).members + first_seq(child).members))
        end

        rule.children = child.children
      end

      flatten_rules(rule)
    end
Flattens a single rule.

 @param rule [Tree::RuleNode] The candidate for flattening
 @see #flatten_rules