code: def instance_throughput_ratio(self, inst_id):
          
          inst_thrp, otherThrp = self.getThroughputs(inst_id)
  
          # Backup throughput may be 0 so moving ahead only if it is not 0
          r = inst_thrp / otherThrp if otherThrp and inst_thrp is not None \
              else None
          return r
docs: The relative throughput of an instance compared to the backup
          instances.