Based on Hack90/ref_seq_viral, using pytrf with settings:
```
pytrf.STRFinder(
  seqdict['id'], seqdict['sequence'],
  mono=5, di=2, tri=2, tetra=2, penta=2, hexa=2
)
```
and contains columns:
```
['id', 'start_pos', 'end_pos', 'motif_seq', 'motif_length', 'repeats', 'ssr_length']
```