diff --git a/paddle/pybind/protobuf.cc b/paddle/pybind/protobuf.cc
index 3388b5cfdc0640237a3ef586535ccf1812845c4e..0a6020d6492f0f6db2d4d9b4769a4dcd2117391e 100644
--- a/paddle/pybind/protobuf.cc
+++ b/paddle/pybind/protobuf.cc
@@ -85,6 +85,7 @@ namespace pybind {
 
 using namespace paddle::framework;  // NOLINT
 
+// convert between std::vector and protobuf repeated.
 template <typename T>
 inline std::vector<T> RepeatedToVector(
     const google::protobuf::RepeatedField<T> &repeated_field) {
@@ -104,6 +105,7 @@ inline void VectorToRepeated(const std::vector<T> &vec,
   }
 }
 
+// Specialize vector<bool>.
 template <typename RepeatedField>
 inline void VectorToRepeated(const std::vector<bool> &vec,
                              RepeatedField *repeated_field) {
@@ -118,13 +120,16 @@ class OpDescBind;
 class BlockDescBind;
 class VarDescBind;
 
+// Each Protobuf Message, we provide a XXXBind class. In that class, we optimize
+// read/write speed. Only when we want the protobuf message, the local changes
+// will be synchronized (by `Sync` method).
 class VarDescBind {
 public:
   explicit VarDescBind(const std::string &name) { desc_.set_name(name); }
 
   VarDesc *Proto() { return &desc_; }
 
-  py::bytes Name() { return desc_.name(); }
+  py::bytes Name() const { return desc_.name(); }
 
   void SetShape(const std::vector<int64_t> &dims) {
     VectorToRepeated(dims, desc_.mutable_lod_tensor()->mutable_dims());
@@ -134,11 +139,13 @@ public:
     desc_.mutable_lod_tensor()->set_data_type(data_type);
   }
 
-  std::vector<int64_t> Shape() {
+  std::vector<int64_t> Shape() const {
     return RepeatedToVector(desc_.lod_tensor().dims());
   }
 
-  framework::DataType DataType() { return desc_.lod_tensor().data_type(); }
+  framework::DataType DataType() const {
+    return desc_.lod_tensor().data_type();
+  }
 
 private:
   VarDesc desc_;
@@ -283,16 +290,16 @@ public:
 
   void SetBlockAttr(const std::string &name, BlockDescBind &block);
 
-  int GetBlockAttr(const std::string &name) const {
+  Attribute GetAttr(const std::string &name) const {
     auto it = attrs_.find(name);
     PADDLE_ENFORCE(it != attrs_.end(), "Attribute %s is not found", name);
-    return boost::get<BlockDesc *>(it->second)->idx();
+    return it->second;
   }
 
-  Attribute GetAttr(const std::string &name) const {
+  int GetBlockAttr(const std::string &name) const {
     auto it = attrs_.find(name);
     PADDLE_ENFORCE(it != attrs_.end(), "Attribute %s is not found", name);
-    return it->second;
+    return boost::get<BlockDesc *>(it->second)->idx();
   }
 
 private:
@@ -312,7 +319,7 @@ public:
   BlockDescBind(const BlockDescBind &o) = delete;
   BlockDescBind &operator=(const BlockDescBind &o) = delete;
 
-  int32_t id() const { return desc_->idx(); }
+  int32_t ID() const { return desc_->idx(); }
 
   int32_t Parent() const { return desc_->parent_idx(); }
 
@@ -410,7 +417,7 @@ public:
 
   BlockDescBind *AppendBlock(const BlockDescBind &parent) {
     auto *b = prog_->add_blocks();
-    b->set_parent_idx(parent.id());
+    b->set_parent_idx(parent.ID());
     b->set_idx(prog_->blocks_size() - 1);
     blocks_.emplace_back(new BlockDescBind(this, b));
     return blocks_.back().get();
@@ -454,6 +461,7 @@ void OpDescBind::SetBlockAttr(const std::string &name, BlockDescBind &block) {
   this->attrs_[name] = desc;
 }
 
+// Bind Methods
 void BindProgramDesc(py::module &m) {
   py::class_<ProgramDescBind>(m, "ProgramDesc", "")
       .def_static("instance",
@@ -481,7 +489,7 @@ void BindProgramDesc(py::module &m) {
 
 void BindBlockDesc(py::module &m) {
   py::class_<BlockDescBind>(m, "BlockDesc", "")
-      .def_property_readonly("id", &BlockDescBind::id)
+      .def_property_readonly("id", &BlockDescBind::ID)
       .def_property_readonly("parent", &BlockDescBind::Parent)
       .def("append_op",
            &BlockDescBind::AppendOp,