message: Remove unused code and imports in `small_net` tests
diff: use std::{
  collections::{HashMap, HashSet},
  fmt::{self, Debug, Display, Formatter},
  - io,
  time::Duration,
  };
  @@ -141,8 +140,6 @@ impl Network {
  &mut self,
  cfg: small_network::Config,
  ) -> anyhow::Result<(NodeId, &mut reactor::Runner<TestReactor>)> {
  - let id = self.node_count;
  -
  let runner: reactor::Runner<TestReactor> = reactor::Runner::new(cfg).await?;
  self.node_count += 1;
  