docs: def et2roc(et_fo, roc_fo):
          """ET to ROC conversion.
  
  		Args:
  			et_fo (file): File object for the ET file.
  			roc_fo (file): File object for the ROC file.
  
  		raises: ValueError
  
  		"""
  
          stats_dicts = [
              {
                  "q": q,
                  "M": 0,
                  "w": 0,
                  "m": 0,
                  "P": 0,
                  "U": 0,
                  "u": 0,
                  "T": 0,
                  "t": 0,
                  "x": 0
              } for q in range(rnftools.lavender.MAXIMAL_MAPPING_QUALITY + 1)
          ]
  
          for line in et_fo:
              line = line.strip()
              if line != "" and line[0] != "#":
                  (read_tuple_name, tab, info_categories) = line.partition("\t")
                  intervals = info_categories.split(",")
                  for interval in intervals:
                      category = interval[0]
                      (left, colon, right) = interval[2:].partition("-")
                      for q in range(int(left), int(right) + 1):
                          stats_dicts[q][category] += 1
  
          roc_fo.write("# Numbers of reads in several categories in dependence" + os.linesep)
          roc_fo.write("# on the applied threshold on mapping quality q" + os.linesep)
          roc_fo.write("# " + os.linesep)
          roc_fo.write("# Categories:" + os.linesep)
          roc_fo.write("#        M: Mapped correctly." + os.linesep)
          roc_fo.write("#        w: Mapped to a wrong position." + os.linesep)
          roc_fo.write("#        m: Mapped but should be unmapped." + os.linesep)
          roc_fo.write("#        P: Multimapped." + os.linesep)
          roc_fo.write("#        U: Unmapped and should be unmapped." + os.linesep)
          roc_fo.write("#        u: Unmapped but should be mapped." + os.linesep)
          roc_fo.write("#        T: Thresholded correctly." + os.linesep)
          roc_fo.write("#        t: Thresholded incorrectly." + os.linesep)
          roc_fo.write("#        x: Unknown." + os.linesep)
          roc_fo.write("#" + os.linesep)
          roc_fo.write("# q\tM\tw\tm\tP\tU\tu\tT\tt\tx\tall" + os.linesep)
  
          l_numbers = []
          for line in stats_dicts:
              numbers = [
                  line["M"], line["w"], line["m"], line["P"], line["U"], line["u"], line["T"], line["t"], line["x"]
              ]
              if numbers != l_numbers:
                  roc_fo.write("\t".join([str(line["q"])] + list(map(str, numbers)) + [str(sum(numbers))]) + os.linesep)
              l_numbers = numbers