       iex> Map.fetch(%{a: 1}, :b)
       :error
 
+  Inlined by the compiler.
   """
   @spec fetch(map, key) :: {:ok, value} | :error
   def fetch(map, key), do: :maps.find(key, map)

      iex> Map.has_key?(%{a: 1}, :b)
      false

  """
  @spec has_key?(map, key) :: boolean
  def has_key?(map, key), do: :maps.is_key(key, map)

      iex> Map.replace!(%{a: 1}, :b, 2)
      ** (KeyError) key :b not found in: %{a: 1}

  Inlined by the compiler.
  """
  @spec replace!(map, key, value) :: map
  def replace!(map, key, value) do
