def extract_script_nodes(list)
      list.select { |item| item.is_a?(::Sass::Script::Tree::Node) }
    end
def extract_script_nodes(list)
      list.select { |item| item.is_a?(::Sass::Script::Tree::Node) }
    end
A number of tree nodes return lists that have strings and
 Sass::Script::Nodes interspersed within them. This returns a filtered list
 of just those nodes.