community: KuzuGraph needs allow_dangerous_requests, add graph documents via LLMGraphTransformer (#27949)

- [x] **PR title**: "community: Kuzu - Add graph documents via
LLMGraphTransformer"
- This PR adds a new method `add_graph_documents` to use the
`GraphDocument`s extracted by `LLMGraphTransformer` and store in a Kùzu
graph backend.
- This allows users to transform unstructured text into a graph that
uses Kùzu as the graph store.

- [x] **Lint and test**: Run `make format`, `make lint` and `make test`
from the root of the package(s) you've modified. See contribution
guidelines for more: https://python.langchain.com/docs/contributing/

---------

Co-authored-by: pookam90 <pookam@microsoft.com>
Co-authored-by: Pooja Kamath <60406274+Pookam90@users.noreply.github.com>
Co-authored-by: hsm207 <hsm207@users.noreply.github.com>
Co-authored-by: Erick Friis <erick@langchain.dev>

libs/community/langchain_community/graphs/kuzu_graph.py

@@ -1,4 +1,7 @@
-from typing import Any, Dict, List
+from hashlib import md5
+from typing import Any, Dict, List, Tuple
+
+from langchain_community.graphs.graph_document import GraphDocument, Relationship
 
 
 class KuzuGraph:
@@ -16,7 +19,19 @@ class KuzuGraph:
         See https://python.langchain.com/docs/security for more information.
     """
 
-    def __init__(self, db: Any, database: str = "kuzu") -> None:
+    def __init__(
+        self, db: Any, database: str = "kuzu", allow_dangerous_requests: bool = False
+    ) -> None:
+        """Initializes the Kùzu graph database connection."""
+
+        if allow_dangerous_requests is not True:
+            raise ValueError(
+                "The KuzuGraph class is a powerful tool that can be used to execute "
+                "arbitrary queries on the database. To enable this functionality, "
+                "set the `allow_dangerous_requests` parameter to `True` when "
+                "constructing the KuzuGraph object."
+            )
+
         try:
             import kuzu
         except ImportError:
@@ -57,7 +72,7 @@ class KuzuGraph:
                 if properties[property_name]["dimension"] > 0:
                     if "shape" in properties[property_name]:
                         for s in properties[property_name]["shape"]:
-                            list_type_flag += "[%s]" % s
+                            list_type_flag += f"[{s}]"
                     else:
                         for i in range(properties[property_name]["dimension"]):
                             list_type_flag += "[]"
@@ -71,7 +86,7 @@ class KuzuGraph:
         rel_tables = self.conn._get_rel_table_names()
         for table in rel_tables:
             relationships.append(
-                "(:%s)-[:%s]->(:%s)" % (table["src"], table["name"], table["dst"])
+                f"(:{table['src']})-[:{table['name']}]->(:{table['dst']})"
             )
 
         rel_properties = []
@@ -93,3 +108,154 @@ class KuzuGraph:
             f"Relationships properties: {rel_properties}\n"
             f"Relationships: {relationships}\n"
         )
+
+    def _create_chunk_node_table(self) -> None:
+        self.conn.execute(
+            """
+            CREATE NODE TABLE IF NOT EXISTS Chunk (
+                id STRING,
+                text STRING,
+                type STRING,
+                PRIMARY KEY(id)
+            );
+            """
+        )
+
+    def _create_entity_node_table(self, node_label: str) -> None:
+        self.conn.execute(
+            f"""
+            CREATE NODE TABLE IF NOT EXISTS {node_label} (
+                id STRING,
+                type STRING,
+                PRIMARY KEY(id)
+            );
+            """
+        )
+
+    def _create_entity_relationship_table(self, rel: Relationship) -> None:
+        self.conn.execute(
+            f"""
+            CREATE REL TABLE IF NOT EXISTS {rel.type} (
+                FROM {rel.source.type} TO {rel.target.type}
+            );
+            """
+        )
+
+    def add_graph_documents(
+        self,
+        graph_documents: List[GraphDocument],
+        allowed_relationships: List[Tuple[str, str, str]],
+        include_source: bool = False,
+    ) -> None:
+        """
+        Adds a list of `GraphDocument` objects that represent nodes and relationships
+        in a graph to a Kùzu backend.
+
+        Parameters:
+          - graph_documents (List[GraphDocument]): A list of `GraphDocument` objects
+            that contain the nodes and relationships to be added to the graph. Each
+            `GraphDocument` should encapsulate the structure of part of the graph,
+            including nodes, relationships, and the source document information.
+
+          - allowed_relationships (List[Tuple[str, str, str]]): A list of allowed
+            relationships that exist in the graph. Each tuple contains three elements:
+            the source node type, the relationship type, and the target node type.
+            Required for Kùzu, as the names of the relationship tables that need to
+            pre-exist are derived from these tuples.
+
+          - include_source (bool): If True, stores the source document
+            and links it to nodes in the graph using the `MENTIONS` relationship.
+            This is useful for tracing back the origin of data. Merges source
+            documents based on the `id` property from the source document metadata
+            if available; otherwise it calculates the MD5 hash of `page_content`
+            for merging process. Defaults to False.
+        """
+        # Get unique node labels in the graph documents
+        node_labels = list(
+            {node.type for document in graph_documents for node in document.nodes}
+        )
+
+        for document in graph_documents:
+            # Add chunk nodes and create source document relationships if include_source
+            # is True
+            if include_source:
+                self._create_chunk_node_table()
+                if not document.source.metadata.get("id"):
+                    # Add a unique id to each document chunk via an md5 hash
+                    document.source.metadata["id"] = md5(
+                        document.source.page_content.encode("utf-8")
+                    ).hexdigest()
+
+                self.conn.execute(
+                    f"""
+                    MERGE (c:Chunk {{id: $id}}) 
+                        SET c.text = $text,
+                            c.type = "text_chunk"
+                    """,  # noqa: F541
+                    parameters={
+                        "id": document.source.metadata["id"],
+                        "text": document.source.page_content,
+                    },
+                )
+
+            for node_label in node_labels:
+                self._create_entity_node_table(node_label)
+
+            # Add entity nodes from data
+            for node in document.nodes:
+                self.conn.execute(
+                    f"""
+                    MERGE (e:{node.type} {{id: $id}})
+                        SET e.type = "entity"
+                    """,
+                    parameters={"id": node.id},
+                )
+                if include_source:
+                    # If include_source is True, we need to create a relationship table
+                    # between the chunk nodes and the entity nodes
+                    self._create_chunk_node_table()
+                    ddl = "CREATE REL TABLE GROUP IF NOT EXISTS MENTIONS ("
+                    table_names = []
+                    for node_label in node_labels:
+                        table_names.append(f"FROM Chunk TO {node_label}")
+                    table_names = list(set(table_names))
+                    ddl += ", ".join(table_names)
+                    # Add common properties for all the tables here
+                    ddl += ", label STRING, triplet_source_id STRING)"
+                    if ddl:
+                        self.conn.execute(ddl)
+
+                    # Only allow relationships that exist in the schema
+                    if node.type in node_labels:
+                        self.conn.execute(
+                            f"""
+                            MATCH (c:Chunk {{id: $id}}),
+                                  (e:{node.type} {{id: $node_id}})
+                            MERGE (c)-[m:MENTIONS]->(e)
+                          SET m.triplet_source_id = $id
+                            """,
+                            parameters={
+                                "id": document.source.metadata["id"],
+                                "node_id": node.id,
+                            },
+                        )
+
+            # Add entity relationships
+            for rel in document.relationships:
+                self._create_entity_relationship_table(rel)
+                # Create relationship
+                source_label = rel.source.type
+                source_id = rel.source.id
+                target_label = rel.target.type
+                target_id = rel.target.id
+                self.conn.execute(
+                    f"""
+                    MATCH (e1:{source_label} {{id: $source_id}}),
+                            (e2:{target_label} {{id: $target_id}})
+                    MERGE (e1)-[:{rel.type}]->(e2)
+                    """,
+                    parameters={
+                        "source_id": source_id,
+                        "target_id": target_id,
+                    },
+                )