code: def parse_script_interpreter(source):
      
      # Find terminating newline. Assume last byte of binprm_buf if absent.
      nl = source.find(b'\n', 0, 128)
      if nl == -1:
          nl = min(128, len(source))
  
      # Split once on the first run of whitespace. If no whitespace exists,
      # bits just contains the interpreter filename.
      bits = source[0:nl].strip().split(None, 1)
      if len(bits) == 1:
          return mitogen.core.to_text(bits[0]), None
      return mitogen.core.to_text(bits[0]), mitogen.core.to_text(bits[1])
docs: Parse the script interpreter portion of a UNIX hashbang using the rules
      Linux uses.
  
      :param str source: String like "/usr/bin/env python".
  
      :returns:
          Tuple of `(interpreter, arg)`, where `intepreter` is the script
          interpreter and `arg` is its sole argument if present, otherwise
          :py:data:`None`.