code: def ifo(self):
          
          if len(self.ifo_list) == 1:
              return self.ifo_list[0]
          else:
              err = "self.ifo_list must contain only one ifo to access the "
              err += "ifo property. %s." %(str(self.ifo_list),)
              raise TypeError(err)
docs: If only one ifo in the ifo_list this will be that ifo. Otherwise an
          error is raised.