def add_line_number(node)
      node.line ||= line if node.is_a?(::Sass::Script::Tree::Node)
      node
    end
def add_line_number(node)
      node.line ||= line if node.is_a?(::Sass::Script::Tree::Node)
      node
    end
The Sass parser sometimes doesn't assign line numbers in cases where it
 should. This is a helper to easily correct that.