can't clone use ssh key

[haofrank]

hi~ I can't use my id_rsa key to clone my repo.
this is my directory structure：
├── code
├── git_test.py
├── id_rsa
├── id_rsa.pub
└── ssh_executable.sh

git_test.py

import os
import git
from git import Repo
from git import Git

git_url = "git@xxx/xxx.git"
git_branch = "master"
out_dir = "./code"

# One
git_ssh_identity_file = os.path.expanduser('./id_rsa')
git_ssh_cmd = 'ssh -i %s' % git_ssh_identity_file

with Git().custom_environment(GIT_SSH_COMMAND=git_ssh_cmd):
  repo = Repo.clone_from(git_url, out_dir, branch="master")
  print("Success")

# Two
ssh_executable = os.path.join("./", 'ssh_executable.sh')

with Git().custom_environment(GIT_SSH=ssh_executable):
  repo = Repo.clone_from(git_url, out_dir, branch="master")
  print("Success")

ssh_executable.sh

#!/bin/sh
ID_RSA="./id_rsa"
exec /usr/bin/ssh -o StrictHostKeyChecking=no -i $ID_RSA "$@"

I tried both methods and could not succeed clone repo....
if I move the id_res id_res.pub to ~/.ssh. it will success. hoping to get your help~

Traceback (most recent call last):
  File "git_test.py", line 15, in <module>
    repo = Repo.clone_from(git_url, out_dir, branch="master")
  File "/Users/frank/miniconda3/lib/python3.7/site-packages/git/repo/base.py", line 988, in clone_from
    return cls._clone(git, url, to_path, GitCmdObjectDB, progress, **kwargs)
  File "/Users/frank/miniconda3/lib/python3.7/site-packages/git/repo/base.py", line 939, in _clone
    finalize_process(proc, stderr=stderr)
  File "/Users/frank/miniconda3/lib/python3.7/site-packages/git/util.py", line 333, in finalize_process
    proc.wait(**kwargs)
  File "/Users/frank/miniconda3/lib/python3.7/site-packages/git/cmd.py", line 415, in wait
    raise GitCommandError(self.args, status, errstr)
git.exc.GitCommandError: Cmd('git') failed due to: exit code(128)
  cmdline: git clone --branch=master -v [email protected] ./code
  stderr: 'Cloning into './code'...
[email protected]: Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

[haofrank]

chmod 400 ~/.ssh/id_rsa
work's fine.