You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: mod.rs
    path of file: ./repos/rust-bert/src/models/longformer
    
    the code of the file until where you have to start completion: //! # Longformer: The Long-Document Transformer (Betalgy et al.)
//!
//! Implementation of the Longformer language model ([Longformer: The Long-Document Transformer](https://arxiv.org/abs/2001.04063) Betalgy, Peters, Cohan, 2020).
//! The base model is implemented in the `longformer_model::LongformerModel` struct. Several language model heads have also been implemented, including:
//! - Masked language model: `longformer_model::LongformerForMaskedLM`
//! - Multiple choices: `longformer_model:LongformerForMultipleChoice`
//! - Question an
    
//! fn main() -> anyhow::Result<()> {
//!    //    Set-up Question Answering model
//!    use rust_bert::pipelines::common::ModelResource;
//! let config = QuestionAnsweringConfig::new(
//!        ModelType::Longformer,
//!        ModelResource::Torch(Box::new(RemoteResource::from_pretrained(
//!            LongformerModelResources::LONGFORMER_BASE_SQUAD1,
//!        ))),
//!        RemoteResource::from_pretrained(
//!            LongformerConfigResources::LONGFORMER_BASE_SQUAD1,
//!        ),
//!        RemoteResource::from_pretrained(
//!            LongformerVocabResources::LONGFORMER_BASE_SQUAD1,
//!        ),
//!        Some(RemoteResource::from_pretrained(
//!            LongformerMergesResources::LONGFORMER_BASE_SQUAD1,
//!        )),
//!        false,
//!        None,
//!        false,
//!    );
//!
//!    let qa_model = QuestionAnsweringModel::new(config)?;
//!
//!    //    Define input
//!    let question_1 = String::from("Where does Amy live ?");
//!    let context_1 = String::from("Amy lives in Amsterdam");
//!    let question_2 = String::from("Where does Eric live");
//!    let context_2 = String::from("While Amy lives in Amsterdam, Eric is in The Hague.");
//!    let qa_input_1 = QaInput {
//!        question: question_1,
//!        context: context_1,
//!    };
//!    let qa_input_2 = QaInput {
//!        question: question_2,
//!        context: context_2,
//!    };
//!
//!    //    Get answer
//!    let answers = qa_model.predict(&[qa_input_1, qa_input_2], 1, 32);
//!    println!("{:?}", answers);
//!    Ok(())
//! }