def att(keys, values, opts={})

      default = opts[:default] || values.first

      val = Array(keys).collect { |key| attribute(key) }.compact.first.to_s

      values.include?(val) ? val : default
    end
def att(keys, values, opts={})

      default = opts[:default] || values.first

      val = Array(keys).collect { |key| attribute(key) }.compact.first.to_s

      values.include?(val) ? val : default
    end
Returns the value for attribute 'key', this value should be present
 in the array list 'values'. If not, the default value is returned.
 By default, the default value is the first element of 'values'.