Add CallableFunction javadoc

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

Author: rnett

tensorflow-core/tensorflow-core-api/src/main/java/org/tensorflow/CallableFunction.java

@@ -20,6 +20,9 @@
 import java.util.Map;
 import org.tensorflow.Signature.TensorDescription;
 
+/**
+ * A function that can be called with tensors.
+ */
 public interface CallableFunction {
 
   /**