To specify a specific version of a package in a Python requirements.txt file, you can add the package name followed by the version number in square brackets. For example:

```
numpy==1.18.1
pandas==0.25.3
```

This will ensure that the specified version of the package is installed when you run `pip install -r requirements.txt`.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence