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: group_by_rolling.rs
    path of file: ./repos/polars/crates/polars-lazy/src/physical_plan/executors
    
    the code of the file until where you have to start completion: use super::*;

#[cfg_attr(not(feature = "dynamic_group_by"), allow(dead_code))]
pub(crate) struct GroupByRollingExec {
    pub(crate) input: Box<dyn Executor>,
    pub(crate) keys: Vec<Arc<dyn PhysicalExpr>>,
    pub(crate) aggs: Vec<Arc<dyn PhysicalExpr>>,
    #[cfg(feature = "dynamic_group_by")
    
unsafe fn update_keys(keys: &mut [Series], groups: &GroupsProxy) {
    match groups {
        GroupsProxy::Idx(groups) => {
            let first = groups.first();
            // we don't use agg_first here, because the group
            // can be empty, but we still want to know the first value
            // of that group
            for key in keys.iter_mut() {
                *key = key.take_unchecked_from_slice(first);
            }
        },
        GroupsProxy::Slice { groups, .. } => {
            for key in keys.iter_mut() {
                let indices = groups.iter().map(|[first, _len]| *first).collect_ca("");
                *key = key.take_unchecked(&indices);
            }
        },
    }
}