Feat: init dataflow. (#9791)

### What problem does this PR solve?

#9790

Close #9782

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

agent/component/__init__.py

@@ -50,8 +50,9 @@ del _package_path, _import_submodules, _extract_classes_from_module
 
 
 def component_class(class_name):
-    m = importlib.import_module("agent.component")
-    try:
-        return getattr(m, class_name)
-    except Exception:
-        return getattr(importlib.import_module("agent.tools"), class_name)
+    for mdl in ["agent.component", "agent.tools", "rag.flow"]:
+        try:
+            return getattr(importlib.import_module(mdl), class_name)
+        except Exception:
+            pass
+    assert False, f"Can't import {class_name}"

agent/component/base.py

@@ -16,7 +16,7 @@
 
 import re
 import time
-from abc import ABC, abstractmethod
+from abc import ABC
 import builtins
 import json
 import os
@@ -410,8 +410,8 @@ class ComponentBase(ABC):
         )
 
     def __init__(self, canvas, id, param: ComponentParamBase):
-        from agent.canvas import Canvas  # Local import to avoid cyclic dependency
-        assert isinstance(canvas, Canvas), "canvas must be an instance of Canvas"
+        from agent.canvas import Graph  # Local import to avoid cyclic dependency
+        assert isinstance(canvas, Graph), "canvas must be an instance of Canvas"
         self._canvas = canvas
         self._id = id
         self._param = param
@@ -528,6 +528,10 @@ class ComponentBase(ABC):
         cpn_nms = self._canvas.get_component(self._id)['upstream']
         return cpn_nms
 
+    def get_downstream(self) -> List[str]:
+        cpn_nms = self._canvas.get_component(self._id)['downstream']
+        return cpn_nms
+
     @staticmethod
     def string_format(content: str, kv: dict[str, str]) -> str:
         for n, v in kv.items():
@@ -556,6 +560,5 @@ class ComponentBase(ABC):
     def set_exception_default_value(self):
         self.set_output("result", self.get_exception_default_value())
 
-    @abstractmethod
     def thoughts(self) -> str:
-        ...
+        raise NotImplementedError()