diff --git a/tianshou/data/.gitignore b/tianshou/data/.gitignore
index 15584ca..0d20b64 100644
--- a/tianshou/data/.gitignore
+++ b/tianshou/data/.gitignore
@@ -1 +1 @@
-.pyc
+*.pyc
diff --git a/tianshou/data/utils.py b/tianshou/data/utils.py
new file mode 100644
index 0000000..d073aeb
--- /dev/null
+++ b/tianshou/data/utils.py
@@ -0,0 +1,21 @@
+# internal key match
+
+def internal_key_match(key, keys):
+    """
+    internal rule for key matching between placeholders and data
+    :param key:
+    :param keys:
+    :return: a bool and a data key
+    """
+    if key == 'advantage':
+        if key in keys:
+            return True, key
+        elif 'return' in keys:
+            return True, 'return'
+        else:
+            return False, None
+    else:
+        if key in keys:
+            return True, key
+        else:
+            return False, None
\ No newline at end of file