code: def get_snmp_value(sess, helper, oid):
          
          snmp_result = sess.get_oids(oid)[0]
          if snmp_result is None:
              helper.exit(summary="No response from device for oid " + oid, exit_code=unknown, perfdata='')
  
          else:
              return snmp_result
docs: return a snmp value or exits the plugin with unknown