Method index_at

dlib/external/pybind11/include/pybind11/numpy.h:1005–1007

    /// May throw if the index would lead to out of bounds access.
    template <typename... Ix>
    ssize_t index_at(Ix... index) const {
        return offset_at(index...) / itemsize();
    }

    /**
     * Returns a proxy object that provides access to the array's data without bounds or