opesearch panick after indexing

warning: `langchain-rust` (example "vector_store_opensearch_ollama") generated 2 warnings (run `cargo fix --example "vector_store_opensearch_ollama"` to apply 2 suggestions)
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.50s
Running `target/debug/examples/vector_store_opensearch_ollama`
added document with id: A4lKM5YBmNSgpsL9__Rz
added document with id: BIlKM5YBmNSgpsL9__Rz
added document with id: BYlKM5YBmNSgpsL9__Rz
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Query> what is rust
thread 'main' panicked at src/vectorstore/opensearch/opensearch.rs:183:14:
called `Option::unwrap()` on a `None` value
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Log from opensearch

`025-04-14T07:54:34,293][INFO ][o.o.p.PluginsService ] [localhost] PluginService:onIndexModule index:[security-auditlog-2025.04.14/5QgeiMh5TKKy_3hwcNabEg]
[2025-04-14T07:54:34,311][INFO ][o.o.p.PluginsService ] [localhost] PluginService:onIndexModule index:[test/Pbd7fZCtRN6ArmB6u0oTDA]
[2025-04-14T07:54:34,333][INFO ][o.o.c.m.MetadataCreateIndexService] [localhost] [test] creating index, cause [api], templates [], shards [1]/[1]
[2025-04-14T07:54:34,334][WARN ][o.o.c.r.a.AllocationService] [localhost] Falling back to single shard assignment since batch mode disable or multiple custom allocators set
[2025-04-14T07:54:34,361][INFO ][o.o.p.PluginsService ] [localhost] PluginService:onIndexModule index:[test/Pbd7fZCtRN6ArmB6u0oTDA]
[2025-04-14T07:54:34,406][WARN ][o.o.c.r.a.AllocationService] [localhost] Falling back to single shard assignment since batch mode disable or multiple custom allocators set
[2025-04-14T07:54:34,437][INFO ][o.o.p.PluginsService ] [localhost] PluginService:onIndexModule index:[security-auditlog-2025.04.14/5QgeiMh5TKKy_3hwcNabEg]
[2025-04-14T07:54:34,443][INFO ][o.o.c.m.MetadataMappingService] [localhost] [security-auditlog-2025.04.14/5QgeiMh5TKKy_3hwcNabEg] create_mapping
[2025-04-14T07:54:34,480][WARN ][o.o.c.r.a.AllocationService] [localhost] Falling back to single shard assignment since batch mode disable or multiple custom allocators set
[2025-04-14T07:54:34,485][INFO ][o.o.p.PluginsService ] [localhost] PluginService:onIndexModule index:[security-auditlog-2025.04.14/5QgeiMh5TKKy_3hwcNabEg]
[2025-04-14T07:54:34,500][INFO ][o.o.p.PluginsService ] [localhost] PluginService:onIndexModule index:[security-auditlog-2025.04.14/5QgeiMh5TKKy_3hwcNabEg]
[`

The panic occurs at src/vectorstore/opensearch/opensearch.rs:183:14 due to an unwrap on a None value. Run the example 'vector_store_opensearch_ollama' with RUST_BACKTRACE=1 to see the full stack trace. Examine the OpenSearch integration code around line 183 to understand what optional value is missing during query execution after indexing.

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