def save(opts = {})
      save_png(opts) if Array(opts[:format]).include? :png
      save_pdf(opts) if Array(opts[:format]).include? :pdf
      self
    end
def save(opts = {})
      save_png(opts) if Array(opts[:format]).include? :png
      save_pdf(opts) if Array(opts[:format]).include? :pdf
      self
    end
DSL method. See http://squib.readthedocs.io