[ONNX] Add verification of duplicate in unsqueeze axes attribute (#2668)

src/ngraph/frontend/onnx_import/op/unsqueeze.cpp

@@ -15,6 +15,8 @@
 //*****************************************************************************
 
 #include <numeric>
+#include <set>
+#include <vector>
 
 #include "exceptions.hpp"
 #include "ngraph/op/reshape.hpp"
@@ -34,9 +36,14 @@ namespace ngraph
                     NodeVector inputs{node.get_ng_inputs()};
                     auto data = inputs.at(0);
                     auto data_shape = data->get_shape();
-                    auto axes = node.get_attribute_value<std::vector<int64_t>>("axes");
+                    auto axes = node.get_attribute_value<std::vector<std::int64_t>>("axes");
 
                     ASSERT_VALID_ARGUMENT(node, !axes.empty()) << "'axes' attribute is mandatory.";
+                    ASSERT_VALID_ARGUMENT(
+                        node,
+                        axes.size() ==
+                            std::set<std::int64_t>(std::begin(axes), std::end(axes)).size())
+                        << "'axes' has a duplicate axis.";
 
                     std::sort(std::begin(axes), std::end(axes), std::less<int64_t>());