code: def parse_int(str_num):
      
      str_num = (str_num or "").strip().upper()
      if not str_num:
          return None
  
      base = 10
      if str_num.startswith('0X'):
          base = 16
          str_num = str_num[2:]
      if str_num.endswith('H'):
          base = 16
          str_num = str_num[:-1]
      if str_num.startswith('$'):
          base = 16
          str_num = str_num[1:]
  
      try:
          return int(str_num, base)
      except ValueError:
          return None
docs: Given an integer number, return its value,
      or None if it could not be parsed.
      Allowed formats: DECIMAL, HEXA (0xnnn, $nnnn or nnnnh)
      :param str_num: (string) the number to be parsed
      :return: an integer number or None if it could not be parsedd