Return header content (doesn't actually print like the C library does).

    https://github.com/thom311/libnl/blob/libnl3_2_25/lib/handlers.c#L34

    Positional arguments:
    nlh -- nlmsghdr class instance.

def print_header_content(nlh):
    """Return header content (doesn't actually print like the C library does).

    https://github.com/thom311/libnl/blob/libnl3_2_25/lib/handlers.c#L34

    Positional arguments:
    nlh -- nlmsghdr class instance.
    """
    answer = 'type={0} length={1} flags=<{2}> sequence-nr={3} pid={4}'.format(
        nl_nlmsgtype2str(nlh.nlmsg_type, bytearray(), 32).decode('ascii'),
        nlh.nlmsg_len,
        nl_nlmsg_flags2str(nlh.nlmsg_flags, bytearray(), 128).decode('ascii'),
        nlh.nlmsg_seq,
        nlh.nlmsg_pid,
    )
    return answer