docs: def parse_breakend(alt_str):
      """Parse breakend and return tuple with results, parameters for BreakEnd
      constructor
      """
      arr = BREAKEND_PATTERN.split(alt_str)
      mate_chrom, mate_pos = arr[1].split(":", 1)
      mate_pos = int(mate_pos)
      if mate_chrom[0] == "<":
          mate_chrom = mate_chrom[1:-1]
          within_main_assembly = False
      else:
          within_main_assembly = True
      FWD_REV = {True: record.FORWARD, False: record.REVERSE}
      orientation = FWD_REV[alt_str[0] == "[" or alt_str[0] == "]"]
      mate_orientation = FWD_REV["[" in alt_str]
      if orientation == record.FORWARD:
          sequence = arr[2]
      else:
          sequence = arr[0]
      return (mate_chrom, mate_pos, orientation, mate_orientation, sequence, within_main_assembly)