CisterMoke

This issue seems the be a result of the following if statement in `Pypher.__getattr__` shown [here ](https://github.com/emehrkay/Pypher/commit/d98e04bea5e6dc92284c725e428e05f967f446c8#diff-6cebb5c735ee72529952a3bcd6457fdbef9fd5a2af2bfe39680bb1a14a9b737dR181-R183). Looks like that was added to support the mathematical operations. Adding the definition...

Upon further inspection I was unable to come up with a proper definition of `__len__` that wouldn't break the tests. I also don't understand why `__getattr__` is defined in such...

Ah it seems I created an issue for the same bug: https://github.com/jmschrei/pomegranate/issues/886