I have a matrix say

```
M = matrix([[0,0,5,3],[3,1,5,4],[4,4,6,2],[4,2,7,8],[5,4,6,6],[7,5,8,9]])
```

do divide the lines in two part 3/3 and construct all the vector composing the two submatrix. I want to know if it is possible to index those vectors ? I know how to do this for one shot

`A=M.delete_columns([1,2,3]).delete_rows([3,4,5])`