translate_singluar_message (GetText::TextDomain)

    # File lib/gettext/textdomain.rb, line 70
        def translate_singluar_message(lang, msgid)
          return "" if msgid == "" or msgid.nil?

          lang_key = lang.to_s

          mofile = nil
          if self.class.cached?
            mofile = @mofiles[lang_key]
          end
          unless mofile
            mofile = load_mo(lang)
          end

          if (! mofile) or (mofile ==:empty)
            return nil
          end

          msgstr = mofile[msgid]
          if msgstr and (msgstr.size > 0)
            msgstr
          elsif msgid.include?("\000")
            # Check "aaa\000bbb" and show warning but return the singluar part.
            ret = nil
            msgid_single = msgid.split("\000")[0]
            mofile.each{|key, val|
              if key =~ /^#{Regexp.quote(msgid_single)}\000/
                # Usually, this is not caused to make po-files from rgettext.
                warn %Q[Warning: n_("#{msgid_single}", "#{msgid.split("\000")[1]}") and n_("#{key.gsub(/\000/, '", "')}") are duplicated.]
                ret = val
                break
              end
            }
            ret
          else
            ret = nil
            mofile.each{|key, val|
              if key =~ /^#{Regexp.quote(msgid)}\000/
                ret = val.split("\000")[0]
                break
              end
            }
            ret
          end
        end