code: def set_prop(self, prop, value, ef=None):
          
          if ef:
              # prop should be restricted to n_decoys, an int, the no. of decoys corresponding to a given FPF.
              # value is restricted to the corresponding enrichment factor and should be a float
              self.ef[prop] = value
          else:
              if prop == 'ensemble':
                  # value is a tuple of strings that gives the ensemble composition
                  self.ensemble = value
              elif prop == 'auc':
                  # value is a float that gives the auc value
                  self.auc = value
docs: set attributes values
          :param prop:
          :param value:
          :param ef:
          :return: