Time-series processor, process() doesn't seem to properly set the self.n_features or self.size() function properly

[jhnwu3]

https://colab.research.google.com/drive/1E2ECK3fRTQcpEV99RqdH_zhrmXdGhZWs?usp=sharing

Tutorial Notebook here should produce this when n_features is not manually set here.

[Logiquo]

Closed by #744