Document use of rawtypes

Signed-off-by: Ryan Nett <[email protected]>

Author: rnett

tensorflow-core/tensorflow-core-api/src/main/java/org/tensorflow/op/CustomGradient.java

@@ -30,6 +30,9 @@
  * reflection. To operate on the {@link org.tensorflow.GraphOperation} directly use {@link
  * RawCustomGradient}.
  *
+ * <p>The type of the op is not checked here, but it is required to match the class given to the
+ * adapter.
+ *
  * @param <T> the type of op this gradient is for.
  */
 @SuppressWarnings("rawtypes")