   Currently the only accepted PID is `self()`.
 
   The returned value will be the effective value used. If no value
-  was set for a given process, then it will not be present in
-  the returned list.
+  was set for a given process, then `nil` is returned.
   """
   @spec get_process_level(pid) :: level() | :all | :none | nil
   def get_process_level(pid) when pid == self() do

  This will take priority over the primary level set, so it can be
  used to increase or decrease verbosity of some parts of the running system.
  """
  @spec put_process_level(pid(), level()) :: :ok
  def put_process_level(pid, level) when pid == self() do
    Process.put(@metadata, Logger.Handler.elixir_level_to_erlang_level(level))
    :ok

      appname |> Application.spec(:modules) |> Logger.put_module_level(level)
  """
  @doc since: "1.13.0"
  @spec put_application_level(atom(), level() | :all | :none) :: :ok | {:error, :not_loaded}
  defdelegate put_application_level(appname, level), to: :logger, as: :set_application_level

  @doc """
