hmm, that is interesting because of inheritance (not sure if that was your intention). for example:

```
>>> from bipy.core.sequence import BiologicalSequence, DNASequence
>>> isinstance(DNASequence('AC'),BiologicalSequence)
```

this could get strange in this case:

```
d = DNASequence('AC')
r = RNASequence('AC')
n = NucleotideSequence('AC')
d == n # True
r == n # True
d == r # False
```

this does make sense semantically, but would it be too confusing to us/our users?