This transformer will take care to generate and append in the response the
features declared in the feature store of the current reranking model,
or a specified feature store. Ex. fl=id,[features store=myStore efi.user_text="ibm"]
store - The feature store to extract features from. If not provided it
will default to the features used by your reranking model. efi.* - External feature information variables required by the features
you are extracting. format - The format you want the features to be returned in. Supports (dense|sparse). Defaults to dense.