min_motif problem

```
>>> import pytrf
>>> name = "test"
>>> seq = "GTAC" * 6
>>> print(pytrf.GTRFinder(name, seq, min_motif=4).as_list())
[]
>>> print(pytrf.GTRFinder(name, seq, min_motif=3).as_list())
[('test', 1, 24, 'GTAC', 4, 6, 24)]
```
The repeat motif is "GTAC", and its length is 4. Why doesn't setting min_motif=4 work?
