The HT_DCPeriod in ta-lib is actually wrong

https://github.com/mementum/bta-lib/blob/master/btalib/indicators/ht_dcperiod.py is the code

See line 108: period = 360 / (RAD2DEG*atan(im / re)) if re and im else period1

it should be re/im as per John Ehlers book. That explains the wild variance in results on Dominant Period between HT_DCPeriod call and the DominantPeriod call of zorro