making arg getters constant (#1121)

src/ngraph/node.cpp

@@ -138,7 +138,7 @@ void Node::set_placement(Placement placement)
     m_placement = placement;
 }
 
-std::shared_ptr<Node> Node::get_argument(size_t index)
+std::shared_ptr<Node> Node::get_argument(size_t index) const
 {
     for (auto& i : get_inputs())
     {
@@ -158,7 +158,7 @@ Node::~Node()
     }
 }
 
-NodeVector Node::get_arguments()
+NodeVector Node::get_arguments() const
 {
     NodeVector result;
     for (auto& i : get_inputs())

src/ngraph/node.hpp

@@ -165,9 +165,9 @@ namespace ngraph
         std::unordered_set<descriptor::Tensor*> liveness_new_list;
         std::unordered_set<descriptor::Tensor*> liveness_free_list;
 
-        virtual NodeVector get_arguments(); //const;
+        virtual NodeVector get_arguments() const;
 
-        std::shared_ptr<Node> get_argument(size_t index);
+        std::shared_ptr<Node> get_argument(size_t index) const;
 
         virtual std::shared_ptr<Node> copy_with_new_args(const NodeVector& new_args) const = 0;
 

src/ngraph/op/get_output_element.cpp

@@ -42,7 +42,7 @@ shared_ptr<Node> op::GetOutputElement::copy_with_new_args(const NodeVector& new_
     return make_shared<GetOutputElement>(new_args.at(0), m_n);
 }
 
-NodeVector op::GetOutputElement::get_arguments()
+NodeVector op::GetOutputElement::get_arguments() const
 {
     return NodeVector{get_inputs().at(0).get_output().get_node()};
 }

src/ngraph/op/get_output_element.hpp

@@ -37,7 +37,7 @@ namespace ngraph
 
             /// \return The index of the tuple element to get.
             size_t get_n() const { return m_n; }
-            virtual NodeVector get_arguments() override;
+            virtual NodeVector get_arguments() const override;
 
         protected:
             virtual void generate_adjoints(autodiff::Adjoints& adjoints,