Allow for arbitrary examples containing DSPy.Images

[isaacbmiller]

Inspired by #1763 and to close #1767.

Supports using, saving, and loading arbitrary python objects containing images inside examples/signatures.

Prior to this you could only use a single dspy.Image in a signature.

The it does this is through changing how dspy.Images are serialized. The example will turn into <DSPY_IMAGE_START>data:...<DSPY_IMAGE_END>

These tags were chosen arbitrarily. A tag based implementation (as opposed to just converting it into { "type": "image_url"...} was chosen because of the way that images are processed inside of Adapters. For text only messages, we can use a messages dictionary with the keys of role: str, content: str.

When you add more than just text, the dictionary becomes role:str, content: List[dict]. Where content contains a list of dicts, each with a type key and a corresponding data key("text" or "image_url").

We need to detect the cases where we have more than just text (done through regex searching the content) and breaking it up into the second content format when an image is detected.

A similar strategy is used for serialization/deserialization, where we just save the base64 inside of the tags as a string.

[JehandadK]

Suggested change

	" images: List[dspy.Image] = dspy.InputField(desc=\"An image\")\n",
	" images: List[dspy.Image] = dspy.InputField(desc=\"A list of images\")\n",

[JehandadK]

Thanks for the PR @isaacbmiller. I tried this branch with this signature and sharing relevant logs here with you:

class CreateTitleAndDescription(dspy.Signature):
    """Taking in a list of images and a category tree to output title, description and attributes."""

    images: List[dspy.Image] = dspy.InputField(desc="list of images about the item")
    categories: str = dspy.InputField(desc="category tree of the item")
    title: str = dspy.OutputField(desc=title_desc)
    description: str = dspy.OutputField(desc=description_desc)

    {
      'role': 'user',
      'content': '[[ ## images ## ]]\n["https://static-sd.mercdn.net/photos/m34859626959_1.jpg", "https://static-sd.mercdn.net/photos/m34859626959_2.jpg", "https://static-sd.mercdn.net/photos/m34859626959_3.jpg"]\n\n[[ ## categories ## ]]\nゲーム・おもちゃ・グッズ > トレーディングカード\n\nRespond with the corresponding output fields, starting with the field `[[ ## title ## ]]`, then `[[ ## description ## ]]`, and then ending with the marker for `[[ ## completed ## ]]`.'
    }

[isaacbmiller]

This will also close #1903 and #1913.

[isaacbmiller]

Tagging @chenmoneygithub to make sure that none of the serialization behavior changes here interfere with your plans

[isaacbmiller]

NOTE: JSONAdapter is still not supported and will be handled in a separate PR

[usmanm]

Hey @isaacbmiller! Do you have a sense for when I should expect this PR to get merged?