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: drop_constraints.rs
    path of file: ./repos/delta-rs/crates/core/src/operations
    
    the code of the file until where you have to start completion: //! Drop a constraint from a table

use std::collections::HashMap;

use chrono::Utc;
use futures::future::BoxFuture;
use ser
    
    async fn drop_invalid_constraint_not_existing() -> DeltaResult<()> {
        let batch = get_record_batch(None, false);
        let write = DeltaOps(create_bare_table())
            .write(vec![batch.clone()])
            .await?;

        let table = DeltaOps(write)
            .drop_constraints()
            .with_constraint("not_existing")
            .await;
        assert!(table.is_err());

        Ok(())
    }