Constant SET_LIMIT_REQUEST 

pub const SET_LIMIT_REQUEST: &str = r#"{
  "limit_down": 1024
}"#;

Documentation, response.

use cuprate_test_utils::rpc::data::other::*;
use serde_json::{to_value, Value};

let value = serde_json::from_str::<Value>(&SET_LIMIT_REQUEST);