docs: def select_regexes(strings, regexes):
      """
      select subset of strings matching a regex
      treats strings as a set
      """
      strings = set(strings)
      select = set()
      if isinstance(strings, collections.Iterable):
          for r in regexes:
              s = set(filter(re.compile('^' + r + '$').search, strings))
              strings -= s
              select |= s
          return select
      else:
          raise ValueError("exclude should be iterable")