community[patch]: Add the ability to pass maps to neo4j retrieval query (#19758)

Makes it easier to flatten complex values to text, so you don't have to
use a lot of Cypher to do it.

libs/community/tests/integration_tests/vectorstores/test_neo4jvector.py

@@ -741,3 +741,29 @@ def test_retrieval_params() -> None:
         Document(page_content="test", metadata={"test": "test1"}),
         Document(page_content="test", metadata={"test": "test1"}),
     ]
+
+
+def test_retrieval_dictionary() -> None:
+    """Test if we use parameters in retrieval query"""
+    docsearch = Neo4jVector.from_texts(
+        texts=texts,
+        embedding=FakeEmbeddings(),
+        pre_delete_collection=True,
+        retrieval_query="""
+        RETURN {
+            name:'John', 
+            age: 30,
+            skills: ["Python", "Data Analysis", "Machine Learning"]} as text, 
+            score, {} AS metadata
+        """,
+    )
+    expected_output = [
+        Document(
+            page_content=(
+                "skills:\n- Python\n- Data Analysis\n- "
+                "Machine Learning\nage: 30\nname: John\n"
+            )
+        )
+    ]
+    output = docsearch.similarity_search("Foo", k=1)
+    assert output == expected_output

libs/community/tests/unit_tests/vectorstores/test_neo4j.py

@@ -1,6 +1,9 @@
 """Test Neo4j functionality."""
 
-from langchain_community.vectorstores.neo4j_vector import remove_lucene_chars
+from langchain_community.vectorstores.neo4j_vector import (
+    dict_to_yaml_str,
+    remove_lucene_chars,
+)
 
 
 def test_escaping_lucene() -> None:
@@ -43,3 +46,22 @@ def test_escaping_lucene() -> None:
         remove_lucene_chars("It is the end of the world. Take shelter~")
         == "It is the end of the world. Take shelter"
     )
+
+
+def test_converting_to_yaml() -> None:
+    example_dict = {
+        "name": "John Doe",
+        "age": 30,
+        "skills": ["Python", "Data Analysis", "Machine Learning"],
+        "location": {"city": "Ljubljana", "country": "Slovenia"},
+    }
+
+    yaml_str = dict_to_yaml_str(example_dict)
+
+    expected_output = (
+        "name: John Doe\nage: 30\nskills:\n- Python\n- "
+        "Data Analysis\n- Machine Learning\nlocation:\n  city: Ljubljana\n"
+        "  country: Slovenia\n"
+    )
+
+    assert yaml_str == expected_output