code: def histogram(args):
      
      from jcvi.graphics.histogram import histogram_multiple
  
      p = OptionParser(histogram.__doc__)
      p.add_option("--bins", dest="bins", default=40, type="int",
              help="number of bins to plot in the histogram [default: %default]")
      opts, args = p.parse_args(args)
  
      if len(args) < 1:
          sys.exit(not p.print_help())
  
      gff_files = args
      # metrics = ("Exon_Length", "Intron_Length", "Gene_Length", "Exon_Count")
      colors = ("red", "green", "blue", "black")
      vmaxes = (1000, 1000, 4000, 20)
      xlabels = ("bp", "bp", "bp", "number")
      for metric, color, vmax, xlabel in zip(metrics, colors, vmaxes, xlabels):
          logging.debug("Parsing files in `{0}`..".format(metric))
          numberfiles = [op.join(metric, op.basename(x).split(".")[0] + ".txt") \
                          for x in gff_files]
  
          histogram_multiple(numberfiles, 0, vmax, xlabel, metric,
                         bins=opts.bins, facet=True, fill=color,
                         prefix=metric + ".")
docs: %prog histogram *.gff
  
      Plot gene statistics based on output of stats. For each gff file, look to
      see if the metrics folder (i.e. Exon_Length) contains the data and plot
      them.