diff --git a/api/core/workflow/nodes/base_node.py b/api/core/workflow/nodes/base_node.py
index b83a0ae19..f42cee4cc 100644
--- a/api/core/workflow/nodes/base_node.py
+++ b/api/core/workflow/nodes/base_node.py
@@ -115,7 +115,7 @@ class BaseNode(ABC):
                 )
 
     @classmethod
-    def extract_variable_selector_to_variable_mapping(cls, config: dict) -> dict[str, list[str]]:
+    def extract_variable_selector_to_variable_mapping(cls, config: dict):
         """
         Extract variable selector to variable mapping
         :param config: node config
@@ -125,14 +125,13 @@ class BaseNode(ABC):
         return cls._extract_variable_selector_to_variable_mapping(node_data)
 
     @classmethod
-    @abstractmethod
-    def _extract_variable_selector_to_variable_mapping(cls, node_data: BaseNodeData) -> dict[str, list[str]]:
+    def _extract_variable_selector_to_variable_mapping(cls, node_data: BaseNodeData) -> Mapping[str, Sequence[str]]:
         """
         Extract variable selector to variable mapping
         :param node_data: node data
         :return:
         """
-        raise NotImplementedError
+        return {}
 
     @classmethod
     def get_default_config(cls, filters: Optional[dict] = None) -> dict:
diff --git a/api/core/workflow/workflow_engine_manager.py b/api/core/workflow/workflow_engine_manager.py
index c3b80c5b9..32f0dbba0 100644
--- a/api/core/workflow/workflow_engine_manager.py
+++ b/api/core/workflow/workflow_engine_manager.py
@@ -389,11 +389,10 @@ class WorkflowEngineManager:
                 environment_variables=workflow.environment_variables,
             )
 
+            if node_cls is None:
+                raise ValueError('Node class not found')
             # variable selector to variable mapping
-            try:
-                variable_mapping = node_cls.extract_variable_selector_to_variable_mapping(node_config)
-            except NotImplementedError:
-                variable_mapping = {}
+            variable_mapping = node_cls.extract_variable_selector_to_variable_mapping(node_config)
 
             self._mapping_user_inputs_to_variable_pool(
                 variable_mapping=variable_mapping,
@@ -473,10 +472,9 @@ class WorkflowEngineManager:
         for node_config in iteration_nested_nodes:
             # mapping user inputs to variable pool
             node_cls = node_classes.get(NodeType.value_of(node_config.get('data', {}).get('type')))
-            try:
-                variable_mapping = node_cls.extract_variable_selector_to_variable_mapping(node_config)
-            except NotImplementedError:
-                variable_mapping = {}
+            if node_cls is None:
+                raise ValueError('Node class not found')
+            variable_mapping = node_cls.extract_variable_selector_to_variable_mapping(node_config)
 
             # remove iteration variables
             variable_mapping = {
@@ -942,7 +940,7 @@ class WorkflowEngineManager:
         return new_value
 
     def _mapping_user_inputs_to_variable_pool(self,
-                                              variable_mapping: dict,
+                                              variable_mapping: Mapping[str, Sequence[str]],
                                               user_inputs: dict,
                                               variable_pool: VariablePool,
                                               tenant_id: str,