text: Title: Custom Strategy Based on My existing TV indicator
  Body: Hi,
  
  First of all thanks for creating a great library, this is a game changer.
  
  I have been predominantly using Trading View, I have build many indicators on TV and use them in my daily trading. You can consider them proprietary Algo which are combination of use of basic building blocks all of which are already present in pandas-ta lib.
  
  So my indicator uses a combination of Previous Day High/Low values, Premarket High/low values, EMAs, candle colors , volume pressure, ADR/ATR , curve , pivot points etc.
  
  In a combination, which then results in a buy/sell signal along with take profit and exit signals
  
  I have also been able to create most of it in my Python code using this lib as individual columns in the DF.
  
  What I don't understand is how to now transfer this price of logic into Strategy Class to take advantage of the watch function etc.
  
  Is there an example where I can pass in a function which creates a result column in the DF ?
  
  
  Regards,
  Idris