text: Title: PPO indicator uses sma instead of ema for fast and slow series
  Body: From my understanding the PPO indicator should be similar to the MACD indicator. The main difference is that the PPO shows percentage results. That means, that for same fast, slow and signal parameters both indicators should have cross-sections between signal and macd line at the same time. In your current implementation the PPO cross-sections differ from the MACD indicator cross-sections. I've checked both indicators on the TradingView and TradingView shows the cross-sections for both indicators at the same time.
  
  When I investigated your code, I noticed that for MACD you are using ema for calculation fast and slow series, but for PPO indicator you are using sma. I think that the PPO should also use the ema.
  