@type t() :: %Poolex.Private.State{
  busy_workers_impl: module(),
  busy_workers_state: nil | Poolex.Workers.Behaviour.state(),
  idle_workers_impl: module(),
  idle_workers_state: nil | Poolex.Workers.Behaviour.state(),
  max_overflow: non_neg_integer(),
  monitors: %{
    required(reference()) => Poolex.Private.Monitoring.kind_of_process()
  },
  overflow: non_neg_integer(),
  pool_id: Poolex.pool_id(),
  supervisor: pid(),
  waiting_callers_impl: module(),
  waiting_callers_state: nil | Poolex.Callers.Behaviour.state(),
  worker_args: [any()],
  worker_module: module(),
  worker_start_fun: atom()
}