pub trait IndexKey {
type ChainTrees: IndexTrees + Send + Sync + Clone;
// Required methods
fn write_db_key(
&self,
trees: &Self::ChainTrees,
block_number: u32,
event_index: u16,
) -> Result<(), Error>;
fn get_key_events(&self, trees: &Self::ChainTrees) -> Vec<Event>;
}