module Playbook::ZIndex

def z_index_props
  selected_index_props = z_index_options.keys.select { |sk| try(sk) }
  return nil unless selected_index_props.present?
  selected_index_props.map do |k|
    index_value = send(k)
    "z_index_#{index_value}" if z_index_values.include? index_value
  end.compact.join(" ")
end