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sdks/python/code_generation/fern/README.md

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+# How to generate new client code for communication with Opik backend
+
+## Pre-requirements
+For either the automatic script or the manual steps:
+- You'll need to install the fern SDK: https://github.com/fern-api/fern
+
+This is a one time process in the local machine generating the code.
+
+## Automatic process
+> [!IMPORTANT]
+> You should generally run this script instead of manual steps below.
+> The only pre-requirement is installing the fern SDK.
+
+The following script automates this whole process:
+```bash
+./scripts/generate_openapi.sh
+```
+
+You simply need to run it from the repository base directory.
+
+## Manual process
+
+These are the manual steps (not recommended), as alternative to the automatic script.
+In this case, it's also a pre-requirement to install the fern SDK.
+Steps:
+1. Execute the `./build_and_run.sh script` from the root of repository
+2. Go to http://localhost:3003/ (URL for backend API specification)
+3. Download openapi specification file - `openapi.yaml`
+4. Put this file into `code_generation/fern/openapi/openapi.yaml` (overwrite it).<br>
+   Note that this path contains the version of the schema from which the code in `src/opik/rest_api` for the SDK was generated. Therefore, it might not be the latest version of the schema.
+5. Run `fern generate` from inside `code_generation/fern` folder. This will generate a python code inside the directory called `sdks` near the `fern` one.
+7. Replace content of `src/opik/rest_api` with the python package inside `sdks` (there will be few nested directories, navigate until you find python files)
+8. Run `pre-commit run --all-files` to format code