Retrieves the list of labels defined for a pretrained AI model (Preset).

Labels represent the possible outputs when the AI model predicts a label based on an input text.

Each label consists of a name and a description. The name provides a short identifier, while the description explains the classification context in more detail.

For AI models that do not have labels by nature (e.g., Extractors), this method returns null. If labels are expected for a given preset type but none are defined, it returns an empty array.