Function get_shareholders_holding_changes 

pub async fn get_shareholders_holding_changes(
    client: &Arc<FutuClient>,
    symbol: &str,
    next_key: Option<String>,
    num: Option<i32>,
    sort_type: Option<i32>,
    sort_column: Option<i32>,
    filter_type: Option<i32>,
) -> Result<String>