text: Title: Caption-Based Image Retrieval Model
  Body: We want to implement the Caption-Based Image Retrieval task from https://api.semanticscholar.org/CorpusID:199453025.
  
  The [COCO](https://cocodataset.org/) and [Flickr30k](https://www.kaggle.com/hsankesara/flickr-image-dataset) datasets contain a large number of images with image captions. The task here is to train a model to pick the right image given the caption. The image must be picked from four images, one of which is the real one, and the other three are other random images from the dataset.
  
  You will have to write `Step`s that produce a `DatasetDict` for Flickr30k and COCO, including code that can produce the negative examples. Each instance will consist of a caption with four images. You will also need to write model that can solve this task. The underlying component for the model will be VilBERT, and the [VQA model](https://github.com/allenai/allennlp-models/blob/main/allennlp_models/vision/models/vision_text_model.py) is probably a good place to steal some code getting started.