docs: def _line_to_entry(self,line):
      """parse the line into entries and keys"""
      f = line.rstrip().split("\t")
      """
      'chrom'
      'chromStart'
      'chromEnd'
      'name'
      'score'
      'strand'
      'thickStart'
      'thickEnd'
      'itemRgb'
      'blockCount'
      'blockSizes'
      'blockStarts'
      """
      return Bed12Fields(
         f[0],
         int(f[1]),
         int(f[2]),
         f[3],
         int(f[4]),
         f[5],
         int(f[6]),
         int(f[7]),
         [int(x) for x in f[8].rstrip(',').split(',')],
         int(f[9]),
         [int(x) for x in f[10].rstrip(',').split(',')],
         [int(x) for x in f[11].rstrip(',').split(',')])