code: def expand_syntax(string):
      
      match = syntax_pattern.search(string)
      if match:
          prefix = string[:match.start()]
          suffix = string[match.end():]
          intervals = match.group(1).split(',')
          for interval in intervals:
              interval_match = interval_pattern.match(interval)
              if interval_match:
                  start = interval_match.group(1)
                  end = (interval_match.group(2) or start).strip('-')
                  for i in _iter_numbers(start, end):
                      for expanded in expand_syntax(prefix + i + suffix):
                          yield expanded
      else:
          yield string
docs: Iterator over all the strings in the expansion of the argument