Prompt:
How can I run inference on a trained ML model using Apache Beam?

Response:
Apache Beam enables efficient inference on both local and remote ML models within your pipelines through the RunInference API. This functionality is available in the Python SDK versions 2.40.0 and later. The Java SDK versions 2.41.0 and later also support the API through Apache Beam’s Multi-language Pipelines framework. The `RunInference` transform performs inference on a `PCollection` of examples using an ML model and outputs a `PCollection` containing both the input examples and the corresponding output predictions.

Key features of the RunInference API include:
* Support for both batch and streaming inference.
* Centralized model management for efficient memory and bandwidth usage.
* Compatibility with multiple model frameworks and model hubs.
* Automatic model refreshing to ensure the latest model version is used.
* GPU support for model inference.

The RunInference API supports a variety of frameworks and model hubs, including TensorFlow, PyTorch, Scikit-learn, XGBoost, Hugging Face, TensorFlow Hub, Vertex AI, TensorRT, and ONNX. Additionally, you can easily integrate custom model frameworks.

To import a model into your Apache Beam pipeline, you will need to configure the `ModelHandler` object, which wraps the underlying model and allows you to set necessary environment variables for inference.

Here is an example of importing a PyTorch model handler for use in your pipeline:

```python
from apache_beam.ml.inference.pytorch_inference import PytorchModelHandlerTensor
from apache_beam.ml.inference.base import RunInference

  model_handler = PytorchModelHandlerTensor(
    # Model handler setup
  )

with pipeline as p:
    predictions = p |  'Read' >> beam.ReadFromSource('a_source')
                    |  'RunInference' >> RunInference(model_handler)
```

If you need to run inference on a model that isn't explicitly supported, you can create your own `ModelHandler` or `KeyedModelHandler` with custom logic to load and use your model. For an example of running inference on a custom model loaded with spaCy, refer to the examples in the Apache Beam GitHub repository.

For recommended patterns and best practices when leveraging Apache Beam for inference tasks, see the 'RunInference Patterns' section in the official documentation.

For comprehensive end-to-end examples of inference with supported model frameworks and model hubs, including examples of using the RunInference API in the Java SDK, see the Apache Beam GitHub repository. Additionally, for an illustration of a composite Python transform integrating the RunInference API with preprocessing and postprocessing from a Beam Java SDK pipeline, you can refer to the Apache Beam official documentation.