 
       iex> Keyword.update([a: 1], :a, 13, &1 * 2)
       [a: 2]
+
       iex> Keyword.update([a: 1], :b, 11, &1 * 2)
       [a: 1, b: 11]
 

      iex> Keyword.put([a: 1, b: 2], :a, 3)
      [a: 3, b: 2]

  """
  @spec put(t, key, value) :: t
  def put(keywords, key, value) when is_atom(key) do

  already exists.

  ## Examples
      iex> Keyword.put_new([a: 1], :b, 2)
      [b: 2, a: 1]

      iex> Keyword.put_new([a: 1, b: 2], :a, 3)
      [a: 1, b: 2]
