diff --git a/python/taichi/lang/field.py b/python/taichi/lang/field.py
index 2a6eb310346d5..e699b2a2b8052 100644
--- a/python/taichi/lang/field.py
+++ b/python/taichi/lang/field.py
@@ -44,7 +44,7 @@ def dtype(self):
         Returns:
             DataType: Data type of each individual value.
         """
-        return self.snode.dtype
+        return self.snode._dtype
 
     @property
     def name(self):
diff --git a/python/taichi/lang/matrix.py b/python/taichi/lang/matrix.py
index cf7bcc4a64e60..b9c208eb80450 100644
--- a/python/taichi/lang/matrix.py
+++ b/python/taichi/lang/matrix.py
@@ -1124,7 +1124,7 @@ def calc_dynamic_index_stride(self):
         length = len(paths[0])
         if any(
                 len(path) != length or ti_core.is_custom_type(path[length -
-                                                                   1].dtype)
+                                                                   1]._dtype)
                 for path in paths):
             return
         for i in range(length):
diff --git a/python/taichi/lang/snode.py b/python/taichi/lang/snode.py
index 7b262a4499056..e2f19b52639e8 100644
--- a/python/taichi/lang/snode.py
+++ b/python/taichi/lang/snode.py
@@ -201,7 +201,7 @@ def _path_from_root(self):
         return res
 
     @property
-    def dtype(self):
+    def _dtype(self):
         """Gets the data type of `self`.
 
         Returns:
@@ -255,15 +255,6 @@ def snode(self):
         """
         return self
 
-    @property
-    def needs_grad(self):
-        """Checks whether `self` has a corresponding gradient :class:`~taichi.lang.SNode`.
-
-        Returns:
-            bool: Whether `self` has a corresponding gradient :class:`~taichi.lang.SNode`.
-        """
-        return self.ptr.has_grad()
-
     def _get_children(self):
         """Gets all children components of `self`.