Sending polars Dataframe via juniper GraphQL

Question

I am trying to send the Polars dataframe over juniper GraphQL, but #[juniper::graphql_object] is complaining about trail bound

the trait bound `Result<HashMap<std::string::String, polars::prelude::DataFrame>, FieldError>: IntoResolvable<'_, __S, _, ()>` is not satisfied
the following other types implement trait `IntoResolvable<'a, S, T, C>`:
  <Result<(&'a <T as GraphQLValue<S2>>::Context, T), FieldError<S1>> as IntoResolvable<'a, S2, T, C>>
  <Result<T, E> as IntoResolvable<'a, S, T, C>>
  <Result<std::option::Option<(&'a <T as GraphQLValue<S2>>::Context, T)>, FieldError<S1>> as IntoResolvable<'a, S2, std::option::Option<T>, C>>

Here is my Rust code.

use juniper::{EmptySubscription,
            FieldResult,
            RootNode,
            EmptyMutation};
use polars::prelude::DataFrame;
use std::collections::HashMap;

pub struct QueryRoot;

#[juniper::graphql_object]
impl QueryRoot {
    fn fetch_data() -> FieldResult<HashMap<String, DataFrame>> {
        // ...
        let data: HashMap<String, DataFrame> = fetch_my_data();
        Ok(data)
    }
}

pub type Schema = RootNode<'static, QueryRoot, EmptyMutation, EmptySubscription>;

pub fn create_schema() -> Schema {
    Schema::new(QueryRoot {}, EmptyMutation::new(), EmptySubscription::new())
}

I am guessing that juniper cannot recognize polar's Dataframe struct as graphqlobject. I am wondering if anyone knows how to fix this compile error. I also tried with serde_json, but no luck so far.