class Selenium::WebDriver::PrintOptions

def page_size=(value)
  predefined_sizes = {
    letter: {width: 21.59, height: 27.94},
    legal: {width: 21.59, height: 35.56},
    a4: {width: 21.0, height: 29.7},
    tabloid: {width: 27.94, height: 43.18}
  }
  case value
  when Symbol
    raise ArgumentError, "Invalid page size: #{value}" unless predefined_sizes.key?(value)
    @page_size = predefined_sizes[value]
  when Hash
    unless value.key?(:width) && value.key?(:height)
      raise ArgumentError, 'Custom page size must include :width and :height'
    end
    @page_size = value
  else
    raise ArgumentError, 'Page size must be a Symbol or a Hash'
  end
end