Add Answer class (#5563)

* add answer class

* inheritance instead of composition

* make answer immutable

* Remove probability field for GenerativeAnswer

* rename Answer classes

* fix name change

* add release notes

haystack/preview/__init__.py

@@ -1,4 +1,4 @@
 from canals.component import component
 from haystack.preview.document_stores.decorator import document_store
-from haystack.preview.dataclasses import Document
+from haystack.preview.dataclasses import Document, ContentType, ExtractedAnswer, GeneratedAnswer, Answer
 from haystack.preview.pipeline import Pipeline, PipelineError, NoSuchDocumentStoreError, load_pipelines, save_pipelines

haystack/preview/dataclasses/__init__.py

@@ -1,3 +1,4 @@
 from haystack.preview.dataclasses.document import Document, ContentType
+from haystack.preview.dataclasses.answer import ExtractedAnswer, GeneratedAnswer, Answer
 
-__all__ = ["Document", "ContentType"]
+__all__ = ["Document", "ContentType", "ExtractedAnswer", "GeneratedAnswer", "Answer"]

haystack/preview/dataclasses/answer.py

@@ -0,0 +1,25 @@
+from typing import Any, Dict, List, Optional
+from dataclasses import dataclass
+from haystack.preview.dataclasses.document import Document
+
+
+@dataclass(frozen=True)
+class Answer:
+    data: Any
+    question: str
+    metadata: Dict[str, Any]
+
+
+@dataclass(frozen=True)
+class ExtractedAnswer(Answer):
+    data: Optional[str]
+    document: Document
+    probability: float
+    start: Optional[int] = None
+    end: Optional[int] = None
+
+
+@dataclass(frozen=True)
+class GeneratedAnswer(Answer):
+    data: str
+    documents: List[Document]

releasenotes/notes/add-v2-answer-class-31bc8d3116922594.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - Add Answer base class for haystack v2
+  - Add GeneratedAnswer and ExtractedAnswer