   Returns the number of schedulers online in the VM.
   """
   @spec schedulers_online :: pos_integer
+  @doc since: "1.3.0"
   def schedulers_online do
     :erlang.system_info(:schedulers_online)
   end

  Inlined by the compiler.
  """
  @spec os_time() :: integer
  def os_time do
    :os.system_time()
  end

  with no limitation and is not monotonic.
  """
  @spec os_time(time_unit) :: integer
  @doc since: "1.3.0"
  def os_time(unit) do
    :os.system_time(normalize_time_unit(unit))
  end
