code: def controlled_value(value)
        return if value.blank?
        ControlledValues.instance.find(@attribute, value) or
          raise ControlledValueError.new("#{@attribute} value '#{value}' is not a recognized controlled value.")
      end
docs: Creates a new ControlledValueFinder for the given attribute.
   The optional YAML properties file name maps input values to controlled values.
  
   @param [Symbol] attribute the CV attribute
   Returns the CV value for the given source value. A case-insensitive lookup
   is performed on the CV.
  
   @param [String, nil] value the CV string value to find
   @raise [ControlledValueError] if the CV was not found
   @see ControlledValues#find