code: def display_name(self):
          
          if self.subject_name:
              return u", ".join( [ u", ".join(
                          [ u"{0}={1}".format(k,v) for k, v in dn_tuple ] )
                              for dn_tuple in self.subject_name ])
          for name_type in ("XmppAddr", "DNS", "SRV"):
              names = self.alt_names.get(name_type)
              if names:
                  return names[0]
          return u"<unknown>"
docs: Get human-readable subject name derived from the SubjectName
          or SubjectAltName field.