Harrison/tfidf parameters (#3481)

Co-authored-by: pao <go5kuramubon@gmail.com>
Co-authored-by: KyoHattori <kyo.hattori@abejainc.com>

tests/integration_tests/retrievers/test_tfidf.py

@@ -0,0 +1,17 @@
+from langchain.retrievers.tfidf import TFIDFRetriever
+
+
+def test_from_texts() -> None:
+    input_texts = ["I have a pen.", "Do you have a pen?", "I have a bag."]
+    tfidf_retriever = TFIDFRetriever.from_texts(texts=input_texts)
+    assert len(tfidf_retriever.docs) == 3
+    assert tfidf_retriever.tfidf_array.toarray().shape == (3, 5)
+
+
+def test_from_texts_with_tfidf_params() -> None:
+    input_texts = ["I have a pen.", "Do you have a pen?", "I have a bag."]
+    tfidf_retriever = TFIDFRetriever.from_texts(
+        texts=input_texts, tfidf_params={"min_df": 2}
+    )
+    # should count only multiple words (have, pan)
+    assert tfidf_retriever.tfidf_array.toarray().shape == (3, 2)