Add a method to get an owned reference from a given reference.

Author: insertinterestingnamehere

dynd/include/utility_functions.hpp

@@ -384,7 +384,21 @@ class py_ref_t {
     }
   }
 
-  py_ref_t<false, not_null> borrow() noexcept { return py_ref<false, not_null>(o, false); }
+  // Return a wrapped borrowed reference to the wrapped reference.
+  py_ref_t<false, not_null> borrow() noexcept
+  {
+    // Assert that the wrapped reference is actually valid if it isn't null.
+    PYDYND_ASSERT_IF(o != nullptr, Py_REFCNT(o) > 0);
+    return py_ref_t<false, not_null>(o, false);
+  }
+
+  // Return a wrapped owned reference referring to the currently wrapped reference.
+  py_ref_t<true, not_null> borrow() noexcept
+  {
+    // Assert that the wrapped reference is actually valid if it isn't null.
+    PYDYND_ASSERT_IF(o != nullptr, Py_REFCNT(o) > 0);
+    return py_ref_t<true, not_null>(o, false);
+  }
 
   // Return a reference to the encapsulated PyObject as a raw pointer.
   // Set the encapsulated pointer to NULL.