def printable_content(attributes=nil, &reference_printer)
      attributes ||= printworthy_attributes
      vh = value_hash(attributes)
      vh.transform_value { |value| printable_value(value, &reference_printer) }
    end
def printable_content(attributes=nil, &reference_printer)
      attributes ||= printworthy_attributes
      vh = value_hash(attributes)
      vh.transform_value { |value| printable_value(value, &reference_printer) }
    end
Returns this domain object's attributes content as an attribute => value hash
 suitable for printing.

 The default attributes are this object's saved attributes. The optional
 reference_printer is used to print a referenced domain object.

 @param [<Symbol>, nil] attributes the attributes to print
 @yield [ref] the reference print formatter
 @yieldparam [Resource] ref the referenced domain object to print
 @return [{Symbol => String}] the attribute => content hash