message: Fix call to backend.placeholder()
diff: @@ -1679,7 +1679,7 @@ class Layer(trackable.Trackable):
  output_shapes = self.compute_output_shape(input_shapes)
  def _make_placeholder_like(shape):
  - ph = backend.placeholder(shape, self.dtype)
  + ph = backend.placeholder(shape=shape, dtype=self.dtype)
  ph._keras_mask = None
  return ph
  