add_findings_bundle example

I noticed this

```
# Add the Bundle to the Malware Subject
subject.add_findings_bundle(bundle)
subject.findings_bundles.bundle = [bundle]
```

in
https://github.com/MAECProject/python-maec/blob/master/examples/package_generation_example.py

What is the purpose of the second instruction? It does not seem to have any effect. 
I am just trying to get a good understanding how to create a MAEC file.
