1{ 2 "topology_description": { 3 "type": "ReplicaSetNoPrimary", 4 "servers": [ 5 { 6 "address": "b:27017", 7 "avg_rtt_ms": 5, 8 "type": "PossiblePrimary" 9 } 10 ] 11 }, 12 "operation": "read", 13 "read_preference": { 14 "mode": "Nearest", 15 "tag_sets": [ 16 {} 17 ] 18 }, 19 "suitable_servers": [], 20 "in_latency_window": [] 21}