code: def _first_line_re():
      
      if isinstance(first_line_re.pattern, str):
          return first_line_re
  
      # first_line_re in Python >=3.1.4 and >=3.2.1 is a bytes pattern.
      return re.compile(first_line_re.pattern.decode())
docs: Return a regular expression based on first_line_re suitable for matching
      strings.