code: def _get_macd(df):
          
          fast = df['close_12_ema']
          slow = df['close_26_ema']
          df['macd'] = fast - slow
          df['macds'] = df['macd_9_ema']
          df['macdh'] = (df['macd'] - df['macds'])
          log.critical("NOTE: Behavior of MACDH calculation has changed as of "
                       "July 2017 - it is now 1/2 of previous calculated values")
          del df['macd_9_ema']
          del fast
          del slow
docs: Moving Average Convergence Divergence
  
          This function will initialize all following columns.
  
          MACD Line (macd): (12-day EMA - 26-day EMA)
          Signal Line (macds): 9-day EMA of MACD Line
          MACD Histogram (macdh): MACD Line - Signal Line
          :param df: data
          :return: None