Upgrade the declarative pipeline for cleaner interface (#51)

tests/test_reader.py

@@ -3,7 +3,7 @@ from pathlib import Path
 from langchain.schema import Document as LangchainDocument
 from llama_index.node_parser import SimpleNodeParser
 
-from kotaemon.documents.base import Document, HaystackDocument
+from kotaemon.documents.base import Document
 from kotaemon.loaders import AutoReader
 
 
@@ -19,10 +19,6 @@ def test_pdf_reader():
     assert isinstance(first_doc, Document)
     assert first_doc.text.lower().replace(" ", "") == "dummypdffile"
 
-    # check conversion output
-    haystack_doc = first_doc.to_haystack_format()
-    assert isinstance(haystack_doc, HaystackDocument)
-
     langchain_doc = first_doc.to_langchain_format()
     assert isinstance(langchain_doc, LangchainDocument)