Heatmap visualization issue

[SiwarBG-2019]

When i try to visualize activation map from the "Activation_49" layer of Faster RCNN based Resnet50, i had this issue "ValueError: Unknown layer: RoiPoolingConv".

My code:
layer_idx = utils.find_layer_idx(model_classifier_only,'activation_49')
print(layer_idx)
heat_map = visualize_activation(model_classifier_only,layer_idx, filter_indices= None, seed_input = None, backprop_modifier='relu')

please i need your help