code: def re_sub(pattern, repl, string, count=0, flags=0, custom_flags=0):
      
      if custom_flags & ReFlags.OVERLAP:
          prev_string = None
          while string != prev_string:
              prev_string = string
              string = re.sub(pattern, repl, string, count, flags)
          return string
      return re.sub(pattern, repl, string, count, flags)
docs: Replace regular expression.
  
      Parameters
      ----------
      pattern : `str` or `_sre.SRE_Pattern`
          Compiled regular expression.
      repl : `str` or `function`
          Replacement.
      string : `str`
          Input string.
      count: `int`
          Maximum number of pattern occurrences.
      flags : `int`
          Flags.
      custom_flags : `int`
          Custom flags.