`return matrix[tri(matrix, k=-1, dtype=bool)]`

...assumes of course the matrix is square. If the matrix isn't square, then you can still use the above but need to be a little more careful:

```python
if matrix.shape[0] == matrix.shape[1]:
    return matrix[tri(matrix, k=-1, dtype=bool)]
else:
    lt = matrix[tri(matrix, k=-1, dtype=bool)]
    if matrix.shape[1] > matrix.shape[0]:
        matrix = matrix.T
    rest = array(matrix[(matrix.shape[0] - matrix.shape[1]):].flat)
    return hstack([lt, rest])
```