def rdf_find_object(id)
      return nil unless rdf_valid?
      rdf.each_statement do |s|
        if s.subject == @iri.to_s
          return s.object if s.object.to_s =~ Regexp.new(id, Regexp::IGNORECASE)
        end
      end
      nil
    end
def rdf_find_object(id)
      return nil unless rdf_valid?
      rdf.each_statement do |s|
        if s.subject == @iri.to_s
          return s.object if s.object.to_s =~ Regexp.new(id, Regexp::IGNORECASE)
        end
      end
      nil
    end
Regexp search to find an object matching a string, if it belongs to @iri
 @param id [String] A string literal used to construct a Regexp
 @return [RDF::URI] The first object matching the Regexp