code: def shift_feature_to_x0(xdata, ydata, x0=0, feature=imax):
      
      i = feature(ydata)
      return xdata-xdata[i]+x0, ydata
docs: Finds a feature in the the ydata and shifts xdata so the feature is centered
      at x0. Returns shifted xdata, ydata. Try me with plot.tweaks.manipulate_shown_data()!
  
      xdata,ydata     data set
      x0=0            where to shift the peak
      feature=imax    function taking an array/list and returning the index of said feature