Associate model versions with runs#

When you track an experiment in Neptune, the run gets a unique ID. By storing the ID of one or more runs in the metadata of a model, you unambiguously connect a given model version with a certain experiment. This helps create a lineage between models and related experiments and data.

To create a model version and associate it with a run:

Import Neptune and initialize a ModelVersion object:
```
import neptune

model_version = neptune.init_model_version(
    model="CLS-PRE", # (1)!
)
```
1. The Neptune ID of the model
To use an existing model version, instead of the model parameter, use the with_id parameter and pass a model version ID:
```
model_version = neptune.init_model_version(
    with_id="CLS-PRE-8",
)
```
How do I find the ID?

The Neptune ID is a unique identifier for the run. The Experiments tab displays it in the leftmost column.

In the run structure, the ID is stored in the system namespace (sys).
- If the run is active, you can obtain its ID with run["sys/id"].fetch(). For example:
```
>>> run = neptune.init_run()
...
>>> run["sys/id"].fetch()
'CLS-26'
```
- If you set a custom run ID, it's stored at sys/custom_run_id:
```
>>> run["sys/custom_run_id"].fetch()
'vigilant-puffin-20bt9'
```
Assign the run ID to a field of your choice.
```
model_version["run/id"] = run["sys/id"].fetch()
```
Tip

If you don't have a connection open to the relevant run, you can:
- Reinitialize the run: run = neptune.init_run(with_id="CLS-14")
- Enter the run ID manually: model_version["run/id"] = "CLS-14"
(optional) It can also be helpful to record the URL of the run:
```
model_version["run/url"] = run.get_url()
```

Result

In Neptune, the run ID is logged in the run/id field of the model version.

You can query the logged values from the model_version object with:

run_id = model_version["run/id"].fetch()

run_url = model_version["run/url"].fetch()