message: Add test for middle_outer_views
diff: @@ -2707,6 +2707,16 @@ mod test {
  assert_eq!(block_iter.next(), None);
  }
  + #[test]
  + fn middle_outer_views() {
  + let size = 11;
  + let csr: CsMat<f64> = CsMat::eye(size);
  + assert_eq!(csr.view().middle_outer_views(1, 3).shape(), (3, size));
  +
  + let csc = csr.to_other_storage();
  + assert_eq!(csc.view().middle_outer_views(1, 3).shape(), (size, 3));
  + }
  +
  #[test]
  fn nnz_index() {
  let mat: CsMat<f64> = CsMat::eye(11);
  