message: adds missing header guard
diff: @@ -30,6 +30,10 @@ THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  ******************************<GINKGO LICENSE>*******************************/
  +#ifndef GKO_CORE_DISTRIBUTED_HELPERS_HPP_
  +#define GKO_CORE_DISTRIBUTED_HELPERS_HPP_
  +
  +
  #include <memory>
  @@ -162,3 +166,6 @@ void vector_dispatch(T* linop, F&& f, Args... args)
  } // namespace detail
  } // namespace gko
  +
  +
  +#endif
  