   end
 
   @doc """
-  Returns the set size.
+  Returns the number of elements in `set`.
+
+  ## Examples
+
+      iex> Set.size(HashSet.new([1, 2, 3]))
+      3
+
   """
   @spec size(t) :: non_neg_integer
   def size(set) do

  end

  @doc """
  Checks if set1's members are all contained in set2.

  ## Examples


  end

  @doc """
  Converts `set` to a list.

  ## Examples

      iex> HashSet.to_list(HashSet.new([1, 2, 3]))
      [1,2,3]

  """
  @spec to_list(t) :: list
  def to_list(set) do
