def is_typography_selector?(node)
        node.is_a?(Sass::Tree::RuleNode) && node.rule[0].start_with?("%f-") rescue false
      end
def is_typography_selector?(node)
        node.is_a?(Sass::Tree::RuleNode) && node.rule[0].start_with?("%f-") rescue false
      end
determines if node is a placeholder selector starting widht the %f- convention for typography rulesets