i1 : M = matrix{{1,2,3},{1,34,45}}

o1 = | 1 2  3  |
     | 1 34 45 |

              2        3
o1 : Matrix ZZ  <--- ZZ

i2 : M_1

o2 = | 2  |
     | 34 |

       2
o2 : ZZ

i3 : toString M_1
stdio:3:1:(3):[0]: error: no method found for applying super to:
                                      2
     argument   :  | 2  | (of class ZZ )
                   | 34 |
