code: def compute_metric(self, components):
          
          numerator = components[RECALL_RELEVANT_RETRIEVED]
          denominator = components[RECALL_RELEVANT]
          if denominator == 0.:
              if numerator == 0:
                  return 1.
              else:
                  raise ValueError('')
          else:
              return numerator/denominator
docs: Compute recall from `components`