add graph base

lang_agent/base.py

@@ -6,4 +6,17 @@ class LangToolBase(ABC):
 
     @abstractmethod
     def get_tool_fnc(self)->List[Callable]:
-        pass
+        pass
+
+
+class GraphBase(ABC):
+    
+    @property
+    @abstractmethod
+    def agent(self):
+        """The agent object that must be provided by concrete implementations."""
+        pass
+    
+    def get_agent(self):
+        """Convenience method to access the agent."""
+        return self.agent