strace shows "$include function ..." in .inputrc was not treated correctly #5

On Ubuntu 20.04, complete log files of strace for python, lftp are attached.

cat .inputrc
$include function rl_custom_isearch /home/user2/git.local/test2/rl_custom_isearch/target/release/librl_custom_isearch.so
"\C-r": rl_custom_isearch

test command:
LD_PRELOAD=/home/user2/git.local/rl_custom_function/target/release/librl_custom_function.so strace -o /tmp/strace.python.txt 'python'

important log messages:
openat(AT_FDCWD, "/home/user2/git.local/rl_custom_function/target/release/librl_custom_function.so", O_RDONLY|O_CLOEXEC) = 3
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libreadline.so.8", O_RDONLY|O_CLOEXEC) = 3

openat(AT_FDCWD, "/home/user2/.inputrc", O_RDONLY) = 3

openat(AT_FDCWD, "function rl_custom_isearch /home/user2/git.local/test2/rl_custom_isearch/target/release/librl_custom_isearch.so", O_RDONLY) = -1 ENOENT (No such file or directory)

The last message showed the syntax of $include function ... in .inputrc was not treated correctly even librl_custom_function.so was preloaded. That caused the portion of "function ... " being loaded as a regular file name.

Any idea what cause the problem ? Thanks

strace.lftp.txt
strace.python.txt