   @spec line(t, t) :: t
   def line(doc1, doc2), do: concat(doc1, concat(:doc_line, doc2))
 
-  @doc """
+  @doc ~S"""
   Folds a list of documents into a document using the given folder function.
 
   The list of documents is folded "from the right"; in that, this function is

    doc_cons(doc1, doc2)
  end

  @doc """
  Concatenates a list of documents returning a new document.

  ## Examples

    doc_group(doc)
  end

  @doc ~S"""
  Inserts a mandatory single space between two documents.

  ## Examples
