docs: case of sml put line

docs/examples/rust/nativeexample/examples/schemaless_insert_line.rs

+use taos_query::common::SchemalessPrecision;
+use taos_query::common::SchemalessProtocol;
+use taos_query::common::SmlDataBuilder;
+
+use crate::AsyncQueryable;
+use crate::AsyncTBuilder;
+use crate::TaosBuilder;
+
+async fn put_line() -> anyhow::Result<()> {
+    // std::env::set_var("RUST_LOG", "taos=trace");
+    std::env::set_var("RUST_LOG", "taos=debug");
+    pretty_env_logger::init();
+
+    let dsn =
+        std::env::var("TDENGINE_ClOUD_DSN").unwrap_or("http://localhost:6041".to_string());
+    log::debug!("dsn: {:?}", &dsn);
+
+    let client = TaosBuilder::from_dsn(dsn)?.build().await?;
+
+    let db = "demo_schemaless_ws";
+
+    client.exec(format!("drop database if exists {db}")).await?;
+
+    client
+        .exec(format!("create database if not exists {db}"))
+        .await?;
+
+    let data = [
+        "measurement,host=host1 field1=2i,field2=2.0 1577837300000",
+        "measurement,host=host1 field1=2i,field2=2.0 1577837400000",
+        "measurement,host=host1 field1=2i,field2=2.0 1577837500000",
+        "measurement,host=host1 field1=2i,field2=2.0 1577837600000",
+    ]
+    .map(String::from)
+    .to_vec();
+
+    // demo with all fields
+    let sml_data = SmlDataBuilder::default()
+        .db(db.to_string())
+        .protocol(SchemalessProtocol::Line)
+        .precision(SchemalessPrecision::Millisecond)
+        .data(data.clone())
+        .ttl(1000)
+        .req_id(100u64)
+        .build()?;
+    assert_eq!(client.put(&sml_data).await?, ());
+
+    // demo omit ttl by default
+    let sml_data = SmlDataBuilder::default()
+        .db(db.to_string())
+        .protocol(SchemalessProtocol::Line)
+        .precision(SchemalessPrecision::Millisecond)
+        .data(data.clone())
+        .req_id(101u64)
+        .build()?;
+    assert_eq!(client.put(&sml_data).await?, ());
+
+    // demo omit ttl and req_id by default
+    let sml_data = SmlDataBuilder::default()
+        .db(db.to_string())
+        .protocol(SchemalessProtocol::Line)
+        .precision(SchemalessPrecision::Millisecond)
+        .data(data.clone())
+        .build()?;
+    assert_eq!(client.put(&sml_data).await?, ());
+
+    // demo omit precision by default
+    let sml_data = SmlDataBuilder::default()
+        .db(db.to_string())
+        .protocol(SchemalessProtocol::Line)
+        .data(data)
+        .req_id(103u64)
+        .build()?;
+    assert_eq!(client.put(&sml_data).await?, ());
+
+    client.exec(format!("drop database if exists {db}")).await?;
+
+    Ok(())
+}