added check for TF implementation

updated test case

Author: atroiano

R/layer-attention.R

@@ -16,6 +16,8 @@
 #' @export
 layer_attention <- function(inputs,use_scale=FALSE, causal = FALSE, batch_size = NULL, dtype = NULL, 
                                 name = NULL, trainable = NULL, weights = NULL) {
+  if (!is_tensorflow_implementation() || !tensorflow::tf_version() >= "1.14")
+    stop("layer_dense_features requires TensorFlow implementation and version >= 1.14")
   create_layer(keras$layers$Attention, inputs, list(
       use_scale = use_scale,
       causal = causal,

tests/testthat/test-layers.R

@@ -498,10 +498,12 @@ test_call_succeeds("layer_separable_conv_1d", required_version = "2.1.3", {
   }
 })
 
-test_call_succeeds('layer_attention',{
-input_1 = layer_input(shape=c(4,5))
-input_2 = layer_input(shape=c(4,5))
-layer_attention(c(input_1,input_2))
+test_call_succeeds('layer_attention'{
+  if (is_tensorflow_implementation() && tensorflow::tf_version() >= "1.14"){
+    input_1 = layer_input(shape=c(4,5))
+    input_2 = layer_input(shape=c(4,5))
+    layer_attention(c(input_1,input_2))
+  }
 })
 
 test_call_succeeds("layer_dense_features", required_version = "2.1.3", {