text: 
  import matplotlib.pyplot as plt
  import pandas as pd
  
  class VSASpread():
      def __init__(self):
          pass
  
      def modHistory(self, df):
          modDf = df.copy()
          closeCol = modDf["close"].values
          highCol = modDf["high"].values
          lowCol = modDf["low"].values
          for i in range(modDf.shape[0]):
              #currentRow = modDf.iloc[i].copy()
              #currentRow["close"] = currentRow["high"] - currentRow["low"]
              #modDf.iloc[i] = currentRow
              closeCol[i] = highCol[i] - lowCol[i]
              #if i % (modDf.shape[0] // 20) == 0:
              #    print( "VSA mod: {:.2%}".format(i / modDf.shape[0]) )
          modDf["close"] = closeCol
          modDf.rename(columns={"close": "vsa_spread"}, inplace=True)
          #modDf.drop( ["open", "high", "low", "real_volume", "spread", "tick_volume", "datetime"], axis=1, inplace=True )
  
          rawDf = df.copy()
          #for col in modDf.columns:
          #    rawDf[col] = modDf[col]
          rawDf["vsa_spread"] = modDf["vsa_spread"]
  
          return rawDf
  
      def checkQuality(self, df):
  
          fig, ax = plt.subplots(nrows=2, ncols=1)
  
          enOpen = df["vsa_spread"].values
          x = [x for x in range(df.shape[0])]
          ax[0].plot(x, enOpen)
  
          rawOpen = df["close"].values
          ax[1].plot(x, rawOpen)
  
          plt.show()
          pass