Implement special treatment for the inbound_nodes format of MultiHead…

…Attention

include/fdeep/import_model.hpp

@@ -1137,11 +1137,35 @@ inline node create_node(const nlohmann::json& inbound_nodes_data)
             inbound_nodes_data));
 }
 
+inline nodes create_multi_head_attention_nodes(const std::vector<nlohmann::json> inbound_nodes_data)
+{
+    assertion(inbound_nodes_data.size() == 1 && inbound_nodes_data.front().size() == 1,
+        "multi_head_attention needs to have exactly one primary inbound node; see https://stackoverflow.com/q/77400589/1866775");
+    const auto inbound_node_data = inbound_nodes_data.front().front();
+    const auto value = inbound_node_data[3]["value"];
+    if (json_obj_has_member(inbound_node_data[3], "key")) {
+        return {
+            node({
+                create_node_connection(inbound_node_data),
+                create_node_connection(value),
+                create_node_connection(inbound_node_data[3]["key"])
+                })};
+    }
+    return {
+        node({
+            create_node_connection(inbound_node_data),
+            create_node_connection(value)
+            })};
+}
+
 inline nodes create_nodes(const nlohmann::json& data)
 {
     assertion(data["inbound_nodes"].is_array(), "no inbound nodes");
     const std::vector<nlohmann::json> inbound_nodes_data =
         data["inbound_nodes"];
+    if (data["class_name"] == "MultiHeadAttention") {
+        return create_multi_head_attention_nodes(inbound_nodes_data);
+    }
     return fplus::transform(create_node, inbound_nodes_data);
 }