@callback broadcast(group :: atom(), msg :: any()) :: :ok

@callback call(pid :: pid(), msg :: any(), timeout :: integer()) :: any()

@callback call(group :: atom(), pid :: pid(), msg :: any(), timeout :: integer()) :: any()

@callback cast(pid :: pid(), msg :: any()) :: :ok

@callback cast(group :: atom(), pid :: pid(), msg :: any()) :: :ok

@callback count(group :: atom()) :: non_neg_integer()

@callback count_all() :: non_neg_integer()

@callback list(group :: atom()) :: [pid()]

@callback list_all() :: [{pid(), atom()}]