   end
 
   @doc """
+  System environment variables.
+
   Returns a list of all environment variables. Each variable is given as a
   `{name, value}` tuple where both `name` and `value` are strings.
   """

  end

  @doc """
  Gets Elixir's stacktrace.

  Notice the Erlang VM (and therefore this function) does not
  return the current stacktrace but rather the stacktrace of the
  latest exception.
  """

  end

  @doc """
  User home directory, exception on error.

  Same as `user_home/0` but raises `System.NoHomeError`
  instead of returning `nil` if no user home is set.
  """
