adding supporting writeups (#617)

Co-authored-by: Deepkant Jain <deepkant.jain@oracle.com>

Author: YashPandit4u

model-group-deployment/heterogeneous_model_group_deployment/heterogenous_model_group_deployment.md

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+# Heterogeneous Model Group Deployment
+
+## Description
+
+A **Heterogeneous Model Group** comprises models built on different ML frameworks, such as PyTorch, TensorFlow, ONNX, etc. This group type allows for the deployment of diverse model architectures within a single serving environment.
+
+> ℹ️ Heterogeneous model groups **do not** require a shared model group artifact, as models in the group may rely on different runtimes.
+
+## Use Case
+
+Ideal for scenarios requiring multiple models with different architectures or frameworks deployed together under a unified endpoint.
+
+## Supported Containers
+
+- **BYOC (Bring Your Own Container)** that satisfies the **BYOC Contract** requirements.
+- Customers are encouraged to use **NVIDIA Triton Inference Server**, which provides built-in support for diverse frameworks.
+
+## Serving Mechanism
+
+- Customers should use the **BYOC** deployment flow.
+- **NVIDIA Triton Inference Server** is recommended for hosting models built with PyTorch, TensorFlow, ONNX Runtime, Custom Python, etc.
+- Each model is routed to its corresponding backend automatically.
+- **Triton** handles load balancing, routing, and execution optimization across model types.
+
+For details on dependency management, refer to the section [Dependency Management for Heterogeneous Model Group](#dependency-management-for-heterogeneous-model-group).
+
+## Heterogeneous Model Group Structure
+
+```json
+{
+  "modelGroupsDetails": {
+    "modelGroupConfigurationDetails": {
+      "modelGroupType": "HETEROGENEOUS"
+    },
+    "modelIds": [
+      {
+        "inferenceKey": "model1",
+        "modelId": "ocid.datasciencemodel.xxx1"
+      },
+      {
+        "inferenceKey": "model2",
+        "modelId": "ocid.datasciencemodel.xxx2"
+      },
+      {
+        "inferenceKey": "model3",
+        "modelId": "ocid.datasciencemodel.xxx3"
+      }
+    ]
+  }
+}
+```
+
+> **Note:**  
+> For **BYOC**, Model Deployment enforces a **contract** that containers must follow:
+> - Must expose a web server.
+> - Must include all runtime dependencies needed to load and run the ML model binaries.
+
+## Dependency Management for Heterogeneous Model Group
+
+> **Note:** This section is applicable only when using the **NVIDIA Triton Inference Server** for Heterogeneous deployments.
+
+### Overview
+
+Triton supports multiple ML frameworks and serves them through corresponding backends.
+
+Triton loads models from one or more **model repositories**, each containing framework-specific models and configuration files.
+
+### Natively Supported Backends
+
+For native backends (e.g., ONNX, TF, PT), models must be organized as per **Triton model repository format**.
+
+#### Sample ONNX Model Directory Structure
+
+```
+model_repository/
+└── onnx_model/
+    ├── 1/
+    │   └── model.onnx
+    └── config.pbtxt
+```
+
+#### Sample `config.pbtxt`
+
+```text
+name: "onnx_model"
+platform: "onnxruntime_onnx"
+input [
+  {
+    name: "input_tensor"
+    data_type: TYPE_FP32
+    dims: [ -1, 3, 224, 224 ]
+  }
+]
+output [
+  {
+    name: "output_tensor"
+    data_type: TYPE_FP32
+    dims: [ -1, 1000 ]
+  }
+]
+```
+
+✅ No dependency conflicts are expected for natively supported models.
+
+### Using Python Backend
+
+For models that are not supported natively, Triton provides a **Python backend**.
+
+#### Python Model Directory Structure
+
+```
+models/
+└── add_sub/
+    ├── 1/
+    │   └── model.py
+    └── config.pbtxt
+```
+
+#### If Python Version Differs (Custom Stub)
+
+If the default Python version is insufficient, compile a **custom Python backend stub**.
+
+```
+models/
+└── model_a/
+    ├── 1/
+    │   └── model.py
+    ├── config.pbtxt
+    └── triton_python_backend_stub
+```
+
+### Models with Custom Execution Environments
+
+Use **Conda-Pack** to bundle all Python dependencies and isolate them per model.
+
+#### Sample Structure with Conda-Pack
+
+```
+models/
+└── model_a/
+    ├── 1/
+    │   └── model.py
+    ├── config.pbtxt
+    ├── env/
+    │   └── model_a_env.tar.gz
+    └── triton_python_backend_stub
+```
+
+#### Add This to `config.pbtxt` for Custom Environment
+
+```text
+name: "model_a"
+backend: "python"
+
+parameters: {
+  key: "EXECUTION_ENV_PATH",
+  value: {string_value: "$$TRITON_MODEL_DIRECTORY/env/model_a_env.tar.gz"}
+}
+```