fix: handle string attributes in graph ontology to prevent TypeError crash (fixes #135)

When the LLM returns ontology attributes as plain strings instead of
dicts, set_ontology() crashes with "TypeError: string indices must be
integers, not 'str'" at attr_def["name"].

Two-layer fix:
1. ontology_generator.py: normalize string attrs to {"name", "type",
   "description"} dicts during validation, so downstream code always
   receives well-formed structures.
2. graph_builder.py: add isinstance guard as a safety net in
   set_ontology() for both entity and edge attribute loops.

Co-Authored-By: Octopus <liyuan851277048@icloud.com>

backend/app/services/graph_builder.py

@@ -233,8 +233,13 @@ class GraphBuilderService:
             annotations = {}
             
             for attr_def in entity_def.get("attributes", []):
-                attr_name = safe_attr_name(attr_def["name"])  # 使用安全名称
+                # LLM may return attributes as strings instead of dicts
-                attr_desc = attr_def.get("description", attr_name)
+                if isinstance(attr_def, str):
+                    attr_name = safe_attr_name(attr_def)
+                    attr_desc = attr_def
+                else:
+                    attr_name = safe_attr_name(attr_def["name"])  # 使用安全名称
+                    attr_desc = attr_def.get("description", attr_name)
                 # Zep API 需要 Field 的 description，这是必需的
                 attrs[attr_name] = Field(description=attr_desc, default=None)
                 annotations[attr_name] = Optional[EntityText]  # 类型注解
@@ -257,8 +262,13 @@ class GraphBuilderService:
             annotations = {}
             
             for attr_def in edge_def.get("attributes", []):
-                attr_name = safe_attr_name(attr_def["name"])  # 使用安全名称
+                # LLM may return attributes as strings instead of dicts
-                attr_desc = attr_def.get("description", attr_name)
+                if isinstance(attr_def, str):
+                    attr_name = safe_attr_name(attr_def)
+                    attr_desc = attr_def
+                else:
+                    attr_name = safe_attr_name(attr_def["name"])  # 使用安全名称
+                    attr_desc = attr_def.get("description", attr_name)
                 # Zep API 需要 Field 的 description，这是必需的
                 attrs[attr_name] = Field(description=attr_desc, default=None)
                 annotations[attr_name] = Optional[str]  # 边属性用str类型

backend/app/services/ontology_generator.py

@@ -432,6 +432,11 @@ class OntologyGenerator:
                 entity_name_map[original_name] = entity["name"]
             if "attributes" not in entity:
                 entity["attributes"] = []
+            # Normalize attributes: LLM may return strings instead of dicts
+            entity["attributes"] = [
+                attr if isinstance(attr, dict) else {"name": attr, "type": "text", "description": attr}
+                for attr in entity["attributes"]
+            ]
             if "examples" not in entity:
                 entity["examples"] = []
             # 确保description不超过100字符
@@ -456,6 +461,11 @@ class OntologyGenerator:
                 edge["source_targets"] = []
             if "attributes" not in edge:
                 edge["attributes"] = []
+            # Normalize attributes: LLM may return strings instead of dicts
+            edge["attributes"] = [
+                attr if isinstance(attr, dict) else {"name": attr, "type": "text", "description": attr}
+                for attr in edge["attributes"]
+            ]
             if len(edge.get("description", "")) > 100:
                 edge["description"] = edge["description"][:97] + "..."