Installation instructions using pip doesn't work

[stativ]

The installation instructions described in the readme:

pip install git+https://github.com/Permify/permify-python.git

ends with the following error because of a missing environment variable:

(.venv) [stativ@luna permify]$ pip install git+https://github.com/Permify/permify-python.git
Collecting git+https://github.com/Permify/permify-python.git
  Cloning https://github.com/Permify/permify-python.git to /tmp/pip-req-build-kjknqo6q
  Running command git clone --filter=blob:none --quiet https://github.com/Permify/permify-python.git /tmp/pip-req-build-kjknqo6q
  Resolved https://github.com/Permify/permify-python.git to commit 1da57e52ab8ce4994c0541515016b7077d0410f2
  Installing build dependencies ... done
  Getting requirements to build wheel ... error
  error: subprocess-exited-with-error
  
  × Getting requirements to build wheel did not run successfully.
  │ exit code: 1
  ╰─> [20 lines of output]
      Traceback (most recent call last):
        File "/home/stativ/development/python/permify/.venv/lib/python3.13/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 389, in <module>
          main()
          ~~~~^^
        File "/home/stativ/development/python/permify/.venv/lib/python3.13/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 373, in main
          json_out["return_val"] = hook(**hook_input["kwargs"])
                                   ~~~~^^^^^^^^^^^^^^^^^^^^^^^^
        File "/home/stativ/development/python/permify/.venv/lib/python3.13/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 143, in get_requires_for_build_wheel
          return hook(config_settings)
        File "/tmp/pip-build-env-8_uu29ev/overlay/lib/python3.13/site-packages/setuptools/build_meta.py", line 331, in get_requires_for_build_wheel
          return self._get_build_requires(config_settings, requirements=[])
                 ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/tmp/pip-build-env-8_uu29ev/overlay/lib/python3.13/site-packages/setuptools/build_meta.py", line 301, in _get_build_requires
          self.run_setup()
          ~~~~~~~~~~~~~~^^
        File "/tmp/pip-build-env-8_uu29ev/overlay/lib/python3.13/site-packages/setuptools/build_meta.py", line 317, in run_setup
          exec(code, locals())
          ~~~~^^^^^^^^^^^^^^^^
        File "<string>", line 25, in <module>
      AttributeError: 'NoneType' object has no attribute 'split'
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
error: subprocess-exited-with-error

× Getting requirements to build wheel did not run successfully.
│ exit code: 1
╰─> See above for output.

note: This error originates from a subprocess, and is likely not a problem with pip.

Setting PACKAGE_VERSION env variable prior installation fixes the problem, eg:

export PACKAGE_VERSION=1.0.2
pip install git+https://github.com/Permify/permify-python.git