> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tatara.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Traces

A trace is a collection of model calls that belong together.

Suppose I want to generate a character image from a character description. I would first generate a visual description of the character and then use that visual description to generate the image. I would want to group these two calls together in a trace.

```python theme={null}
with tatara.start_trace(event="create_character_image"):
    with tatara.start_span(event=visual_description_event_name):
        character_visual_description = generate_visual_description(character_description, openai_client)
    with tatara.start_span(event=image_event_name, parent_event=visual_description_event_name):
        character_image = generate_character_image(character_visual_description, openai_client)
```

You can also pass in a `user_id` and an `id_` to the `start_trace` function to associate the trace with your user and to give the trace a unique identifier that you can use to join it to other data.

```python theme={null}
with tatara.start_trace(event="create_character_image", user_id="user_id", id_="trace_id"):
```