Suggestion: Include "labels" in print_block, print_blocks

[pcchen]

Currently, there is no label information in print_block and print_blocks. I would like to suggest to add label information.

Current behaviour:

========================
BLOCK [#2]
 |- []   : Qn index 
 |- Sym(): Qnum of correspond symmetry
                  -----------
                  |         |
   [1] U1(-1)  -->| 1     2 |-->  [1] U1(0)
                  |         |
   [0] U1(1)   -->| 1       |
                  |         |
                  -----------

Total elem: 2
type  : Double (Float64)
cytnx device: CPU
Shape : (1,1,2)
[[[0.00000e+00 0.00000e+00 ]]]

Suggest behaviour:

========================
BLOCK [#2]
 |- []   : Qn index 
 |- Sym(): Qnum of correspond symmetry
                  -----------
                  |         |
   [1] U1(-1)  a-->| 1     2 |-->c  [1] U1(0)
                  |         |
   [0] U1(1)   b-->| 1       |
                  |         |
                  -----------

Total elem: 2
type  : Double (Float64)
cytnx device: CPU
Shape : (1,1,2)
[[[0.00000e+00 0.00000e+00 ]]]