diff --git a/dpgen2/exploration/task/task.py b/dpgen2/exploration/task/task.py
index 3795d897..24f7d02f 100644
--- a/dpgen2/exploration/task/task.py
+++ b/dpgen2/exploration/task/task.py
@@ -54,18 +54,3 @@ def files(self) -> Dict:
             The dict storing all files for the task. The file name is a key of the dict, and the file content is the corresponding value.
         """
         return self._files
-
-
-class FooTask(ExplorationTask):
-    def __init__(
-        self,
-        conf_name="conf.lmp",
-        conf_cont="",
-        inpu_name="in.lammps",
-        inpu_cont="",
-    ):
-        super().__init__()
-        self._files = {
-            conf_name: conf_cont,
-            inpu_name: inpu_cont,
-        }
diff --git a/dpgen2/exploration/task/task_group.py b/dpgen2/exploration/task/task_group.py
index 947fd8e7..964a9cd3 100644
--- a/dpgen2/exploration/task/task_group.py
+++ b/dpgen2/exploration/task/task_group.py
@@ -77,6 +77,21 @@ def make_task(self):
         raise NotImplementedError("This class is not supposed to supply make_task")
 
 
+class FooTask(ExplorationTask):
+    def __init__(
+        self,
+        conf_name="conf.lmp",
+        conf_cont="",
+        inpu_name="in.lammps",
+        inpu_cont="",
+    ):
+        super().__init__()
+        self._files = {
+            conf_name: conf_cont,
+            inpu_name: inpu_cont,
+        }
+
+
 class FooTaskGroup(ExplorationTaskGroup):
     def __init__(self, numb_task):
         super().__init__()