The problem is that random seed will do

```
            if isinstance(a, str):
                a = a.encode()
            a += _sha512(a).digest()
            a = int.from_bytes(a, 'big')
```

and that will modify the bytearray in place.

>>> a = bytearray("1234", "utf-8")
>>> a += b"digest"
>>> a
bytearray(b'1234digest')


IMHO, seed shouldn't modify the input. Since str, and bytes are immutable that will only happen when passing a bytearray which is not consistent.