def _normalize_joliet_path(self, joliet_path):
        # type: (str) -> bytes
        '''
        An internal method to check whether this ISO does or does not require
        a Joliet path.  If a Joliet path is required, the path is normalized
        and returned.

        Parameters:
         joliet_path - The joliet_path to normalize (if necessary).
        Returns:
         The normalized joliet_path if this ISO has Joliet, None otherwise.
        '''
        tmp_path = b''
        if self.joliet_vd is not None:
            if not joliet_path:
                raise pycdlibexception.PyCdlibInvalidInput('A Joliet path must be passed for a Joliet ISO')
            tmp_path = utils.normpath(joliet_path)
        else:
            if joliet_path:
                raise pycdlibexception.PyCdlibInvalidInput('A Joliet path can only be specified for a Joliet ISO')

        return tmp_path
An internal method to check whether this ISO does or does not require
        a Joliet path.  If a Joliet path is required, the path is normalized
        and returned.

        Parameters:
         joliet_path - The joliet_path to normalize (if necessary).
        Returns:
         The normalized joliet_path if this ISO has Joliet, None otherwise.