Haystack, a question answering system, can be extended with various nodes to leverage pre-trained Transformer-based language models. The Classification node can classify answer candidates and add metadata labels such as sentiment analysis or named entity recognition. The Summarizer node uses a pre-trained model to create summaries of documents returned by the Retriever. The Generator node allows creating answers from scratch, working in tandem with dense passage retrieval (DPR) method. These nodes can be combined to create a more efficient and accurate question answering system, enabling features such as sentiment analysis, summarization, natural language generation, and multilingual support.