Langchain::DependencyHelper doesn't respect .gemspec of a gem depending on langchainrb

[ms-ati]

Describe the bug

Consider a gem which depends on langchainrb.

• Langchain::DependencyHelper does not look in the gemspec dependencies of the current gem being developed, forcing LLM dependencies (e.g. aws-sdk-bedrockruntime) to be duplicated in the Gemfile as well.

To Reproduce

Create a gem depending on langchainrb with a .gemspec containing:

spec.add_dependency 'aws-sdk-bedrockruntime'
spec.add_dependency 'langchainrb'  

Observe this error when initializing a Langchain::LLM::AwsBedrock:

~/.gem/ruby/3.3.2/gems/langchainrb-0.19.1/lib/langchain/dependency_helper.rb:38:in `rescue in depends_on': Could not load aws-sdk-bedrockruntime. Please ensure that the aws-sdk-bedrockruntime gem is installed. (Langchain::DependencyHelper::LoadError)
        from ~/.gem/ruby/3.3.2/gems/langchainrb-0.19.1/lib/langchain/dependency_helper.rb:17:in `depends_on'
        from ~/.gem/ruby/3.3.2/gems/langchainrb-0.19.1/lib/langchain/llm/aws_bedrock.rb:46:in `initialize'
        from bin/console:36:in `new'
        from bin/console:36:in `<main>'

To resolve, one must add aws-sdk-bedrockruntime to the Gemfile, as the .gemspec is not consulted in Langchain::DependencyHelper.

Expected behavior

Expected DependencyHelper to find dependencies listed in the gemspec of the gem which depends on langchainrb.

[andreibondarev]

@ms-ati Is this a public open source gem that you're developing?