ImportError: cannot import name 'SubGraph' from 'NodeGraphQt.base.node'

Line 829 of NodeGraphQt > base > **utils.py** has the following line:

`from .node import BaseNode, SubGraph`

and it should probably be changed to the following, since SubGraph appears to have moved to the **graph.py** file:

```
from .node import BaseNode
from .graph import SubGraph
```

More info:
I am running on MacOS 10.15.4 using Python 3.7 in a virtual environment.