How to add search query term to the input for ml_inference processor

Versions (relevant - OpenSearch/Dashboard/Server OS/Browser):
2.17 AWS OS

Describe the issue:
I’d like to add query search term as input in the ml_inference processor. I followed the example here: ML inference (response) - OpenSearch Documentation

My processor is as follows:

PUT /_search/pipeline/my_pipeline_request_review_llm
{
  "response_processors": [
    {
      "ml_inference": {
        "tag": "ml_inference",
        "description": "This processor is going to run llm",
        "model_id": "GzeEVZMB-kzw4OgFUNaB",
        "function_name": "REMOTE",
        "input_map": [
          {
            "context": "title",
            "question": "$._request.query.term.title.value"
          }
        ],
        "output_map": [
          {
            "ext.ml_inference.llm_response": "generated_text"
          }
        ],
        "model_config": {
          "prompt": "Based on following context: ${parameters.context.toString()}. Answer the question: ${parameters.question.toString()} ?"
        },
        "ignore_missing": false,
        "ignore_failure": false
      }
    }
  ]
}

Running search:

GET test_tech_news2/_search?search_pipeline=my_pipeline_request_review_llm
{
  "_source": ["title"],
  "query": {
    "term": {
      "title": {
        "value": "Sample Document"
      }
    }
  }
}

I get the following response:

  "error": {
    "root_cause": [
      {
        "type": "illegal_argument_exception",
        "reason": "cannot find all required input fields: [title, $._request.query.term.title.value] in hit:{\n  \"_index\" : \"test_tech_news2\",\n  \"_id\" : \"K8PXopMBNsmyby02l4zY\",\n  \"_score\" : 0.2876821,\n  \"_source\" : {\n    \"title\" : \"Sample Document\"\n  }\n}"
      }
    ],
    "type": "illegal_argument_exception",
    "reason": "cannot find all required input fields: [title, $._request.query.term.title.value] in hit:{\n  \"_index\" : \"test_tech_news2\",\n  \"_id\" : \"K8PXopMBNsmyby02l4zY\",\n  \"_score\" : 0.2876821,\n  \"_source\" : {\n    \"title\" : \"Sample Document\"\n  }\n}"
  },
  "status": 400
}

For some reason it’s not letting me use $._request.query.term.title.value here. I tried a few workaround but none have worked so far.

Please help

Configuration:

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