Working dummy example for custom LLM endpoint integration

How would a working dummy example work for the scenario of an own LLM like in this README.md https://github.com/explosion/spacy-llm/blob/main/usage_examples/README.md when running it with the proposed config file and adding the dummy RandomClassification.v1 I get this error:

>
> Exception has occurred: AssertionError
> exception: no description

```
from spacy_llm.registry import registry
import random
from typing import Iterable

@registry.llm_models("RandomClassification.v1")
def random_textcat(labels: str):
labels = labels.split(",")
def _classify(prompts: Iterable[str]) -> Iterable[str]:
for _ in prompts:
yield random.choice(labels)

return _classify
...
[components.llm.task]
@llm_tasks = "spacy.TextCat.v1"
labels = LABEL1,LABEL2,LABEL3

[components.llm.model]
@llm_models = "RandomClassification.v1"
labels = ${components.llm.task.labels} # Make sure to use the same label
```