def _check_d1_characters(name):
    # type: (bytes) -> None
    '''
    A function to check that a name only uses d1 characters as defined by ISO9660.

    Parameters:
     name - The name to check.
    Returns:
     Nothing.
    '''
    bytename = bytearray(name)
    for char in bytename:
        if char not in _allowed_d1_characters:
            raise pycdlibexception.PyCdlibInvalidInput('ISO9660 filenames must consist of characters A-Z, 0-9, and _')
A function to check that a name only uses d1 characters as defined by ISO9660.

    Parameters:
     name - The name to check.
    Returns:
     Nothing.