AttributeError: ‘url’ has no attribute ‘urlretrieve’ when calcutating AAindex

Attribution error arose when I tried following sample code.

```python
from PyBioMed.PyProtein import AAIndex
aaidx = AAIndex.GetAAIndex1('KRIW790103')

>AttributeError: ‘urllib’ has no attribute ‘urlretrieve’
```
GetAAIndex1 function had  correctly worked when I used ```urllib.request.urlretrieve``` in AAIndex.py.