Review comments

src/ngraph/autodiff/adjoints.cpp

@@ -82,7 +82,7 @@ autodiff::Adjoints::Adjoints(const std::shared_ptr<Node>& y, const std::shared_p
     // Pass 1 determines which nodes contribute to y as well as setting up a reverse
     // topological sort.
 
-    // Number of nodes that use the a node's value
+    // Number of nodes that use the node's value
     std::unordered_map<std::shared_ptr<Node>, size_t> parent_counts;
 
     // Nodes that have been processed

src/ngraph/node.hpp

@@ -39,6 +39,7 @@ namespace ngraph
     /// view or a (possibly empty) tuple of values.
     class Node : public std::enable_shared_from_this<Node>
     {
+        // So Adjoints can call generate_adjoints
         friend class autodiff::Adjoints;
 
     protected: