Minor tweaks (#11060)

### What problem does this PR solve?

Minor tweaks

### Type of change

- [x] Refactoring

---------

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

agent/component/__init__.py

@@ -13,7 +13,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 #
-
+import logging
 import os
 import importlib
 import inspect
@@ -50,9 +50,10 @@ del _package_path, _import_submodules, _extract_classes_from_module
 
 
 def component_class(class_name):
-    for mdl in ["agent.component", "agent.tools", "rag.flow"]:
+    for module_name in ["agent.component", "agent.tools", "rag.flow"]:
         try:
-            return getattr(importlib.import_module(mdl), class_name)
-        except Exception:
+            return getattr(importlib.import_module(module_name), class_name)
+        except Exception as e:
+            logging.warning(f"Can't import module: {module_name}, error: {e}")
             pass
     assert False, f"Can't import {class_name}"

agent/component/base.py

@@ -514,6 +514,7 @@ class ComponentBase(ABC):
     def get_param(self, name):
         if hasattr(self._param, name):
             return getattr(self._param, name)
+        return None
 
     def debug(self, **kwargs):
         return self._invoke(**kwargs)
@@ -521,7 +522,7 @@ class ComponentBase(ABC):
     def get_parent(self) -> Union[object, None]:
         pid = self._canvas.get_component(self._id).get("parent_id")
         if not pid:
-            return
+            return None
         return self._canvas.get_component(pid)["obj"]
 
     def get_upstream(self) -> List[str]:
@@ -546,7 +547,7 @@ class ComponentBase(ABC):
 
     def exception_handler(self):
         if not self._param.exception_method:
-            return
+            return None
         return {
             "goto": self._param.exception_goto,
             "default_value": self._param.exception_default_value