Improve transformation of inputs passed to Function.create()

[aron]

Currently we only convert URLPath instances into URL strings if passed directly as an input parameter. We want to ensure that we convert all instances of URLPaths provided otherwise we get JSON encoding errors.

The most common use of this is passing a list of files that were output from another model. Here is a minimal reproduction:

# /// script
# requires-python = ">=3.12"
# dependencies = [
#     "replicate>=2b3",
# ]
# ///

import replicate
from replicate.lib._predictions_use import URLPath

video_stitcher = replicate.use("andreasjansson/video-stitcher")


def main() -> None:
    output = video_stitcher(
        videos=[
            URLPath(
                "https://replicate.delivery/xezq/ueemmhGfowaxnp2zx4rQAwZWkIGMkeoEFGwDMB8FJDDUPGiTB/tmpsam6b5v3.mp4"
            ),
            URLPath(
                "https://replicate.delivery/xezq/yitkxodvCK7eJK9BFufsMBaHIfnHgJhlNNIiaQi8g8QebGiTB/tmpby0sgn7w.mp4"
            ),
        ]
    )
    print("output", output)


if __name__ == "__main__":
    main()

This can be run with:

uv run main.py
> TypeError: Object of type URLPath is not JSON serializable

This PR attempts to transform the most common Python data structures into either lists or dicts and in doing so extracts the underlying URL value from any URL path instances.

Note

This might be better implemented as a custom JSON encoder.