code: def overlay_histogram(df, path, palette=None):
      
      if palette is None:
          palette = plotly.colors.DEFAULT_PLOTLY_COLORS * 5
  
      hist = Plot(path=path + "NanoComp_OverlayHistogram.html",
                  title="Histogram of read lengths")
      hist.html, hist.fig = plot_overlay_histogram(df, palette, title=hist.title)
      hist.save()
  
      hist_norm = Plot(path=path + "NanoComp_OverlayHistogram_Normalized.html",
                       title="Normalized histogram of read lengths")
      hist_norm.html, hist_norm.fig = plot_overlay_histogram(
          df, palette, title=hist_norm.title, histnorm="probability")
      hist_norm.save()
  
      log_hist = Plot(path=path + "NanoComp_OverlayLogHistogram.html",
                      title="Histogram of log transformed read lengths")
      log_hist.html, log_hist.fig = plot_log_histogram(df, palette, title=log_hist.title)
      log_hist.save()
  
      log_hist_norm = Plot(path=path + "NanoComp_OverlayLogHistogram_Normalized.html",
                           title="Normalized histogram of log transformed read lengths")
      log_hist_norm.html, log_hist_norm.fig = plot_log_histogram(
          df, palette, title=log_hist_norm.title, histnorm="probability")
      log_hist_norm.save()
  
      return [hist, hist_norm, log_hist, log_hist_norm]
docs: Use plotly to create an overlay of length histograms
      Return html code, but also save as png
  
      Only has 10 colors, which get recycled up to 5 times.