def _internal_is_knet_ascii(buf):
    """
    Checks if the file is a valid K-NET/KiK-net ASCII file.

    :param buf: File to read.
    :type buf: Open file or open file like object.
    """
    first_string = buf.read(11).decode()
    # File has less than 11 characters
    if len(first_string) != 11:
        return False
    if first_string == 'Origin Time':
        return True
    return False