llms/bedrock: Fixed error when using Claude3 model and giving MessageContent with images

[mashiike]

The problem want to solve with this PR

This PR concerns the execution of a prompt to recognize images using llms/bedrock's Claude3 model. In this PR, I would like to address some errors that occur when executing the following code.

package main

import (
	"context"
	_ "embed"
	"log"

	"github.com/tmc/langchaingo/llms"
	"github.com/tmc/langchaingo/llms/bedrock"
	"github.com/tmc/langchaingo/schema"
)

//go:embed image.png
var image []byte

func main() {
	llm, err := bedrock.New(
		bedrock.WithModel(bedrock.ModelAnthropicClaudeV3Haiku),
	)
	if err != nil {
		log.Fatal(err)
	}
	ctx := context.Background()
	resp, err := llm.GenerateContent(
		ctx,
		[]llms.MessageContent{
			{
				Role: schema.ChatMessageTypeHuman,
				Parts: []llms.ContentPart{
					llms.BinaryPart("image/png", image),
					llms.TextPart("Please text what is written on this image."),
				},
			},
		},
	)
	if err != nil {
		log.Fatal(err)
	}
	for _, choice := range resp.Choices {
		log.Println(choice.Content)
	}
}

The code itself is simple, interpreting the image/png image given in the embedding as text.

The errors that occur are the following two types of errors that occur when executing this code.

• 2024/03/22 11:23:14 operation error Bedrock Runtime: InvokeModel, https response error StatusCode: 400, RequestID: 0fa522ef-9201-4f62-9f69-f40ff9046896, ValidationException: messages.0.content.0.image.source: Input tag 'image' found using 'type' does not match any of the expected tags: 'base64'
• 2024/03/22 11:37:33 operation error Bedrock Runtime: InvokeModel, https response error StatusCode: 400, RequestID: 5741321f-54e4-4ef0-9351-d28eb104ee07, ValidationException: messages: roles must alternate between "user" and "assistant", but found multiple "user" roles in a row

The specifications for this area are described in the following document.

https://docs.anthropic.com/claude/reference/claude-on-amazon-bedrock
https://docs.anthropic.com/claude/reference/messages_post

PR Checklist

• Read the Contributing documentation.
• Read the Code of conduct documentation.
• Name your Pull Request title clearly, concisely, and prefixed with the name of the primarily affected package you changed according to Good commit messages (such as memory: add interfaces for X, Y or util: add whizzbang helpers).
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. Fixes #123).
• Describes the source of new concepts.
• References existing implementations as appropriate.
• Contains test coverage for new functions.
• Passes all golangci-lint checks.

[tmc]

Lovely contribution, thank you. Please consider including the sample above as either an example program or even as a documentation site page, I think it would be helpful to others.

I welcome your contributions! please consider driving up line coverage and including in-line comments that explain rationale for subtle parts.