template < typename T >
        class Filterbank{

            public:

                typedef std::unique_ptr<Kernel2D<T> > KernelPtr;

                Filterbank();
                Filterbank( Filterbank<T> && );
                ~Filterbank();

                friend void swap <>( Filterbank<T> &, Filterbank<T> & );
                Filterbank<T> & operator =( Filterbank<T> && );

                const std::unique_ptr<Kernel2D<T> > & at ( int ) const;

                int size() const;

                friend Filterbank<T> createTextonBoostFilterbank <> ( double );

            private:

                std::vector< KernelPtr > m_Bank; // error here!!!
        };

        template < typename T >
        class FilterbankDescriptor : public Descriptor<T>{

            public:

                FilterbankDescriptor();
                FilterbankDescriptor( const Filterbank<T> & );
                FilterbankDescriptor( const FilterbankDescriptor<T> & );
                FilterbankDescriptor( FilterbankDescriptor<T> && );
                ~FilterbankDescriptor();

                virtual std::unique_ptr<Descriptor<T> > clone() const;
                virtual std::unique_ptr<Descriptor<T> > create() const;

                virtual FeatureImage<T> describe(const Matrix<T> &, const std::string & ) const;
                virtual FeatureImage<T> describe(const FeatureImage<T> &, const std::string & ) const;

            private:

                Filterbank<T> m_Bank; // error here!

        };