   end
 
   defp occurrences(key, list) do
-    length(:lists.filter(fn(el) -> el == key end, list))
+    length(:lists.filter(fn el -> el == key end, list))
   end
 
   # Merge

  defp check_impls_for_overridable(module, tuples) do
    table = data_table_for(module)
    impls = :ets.lookup_element(table, {:elixir, :impls}, 2)
    {overridable_impls, impls} = :lists.splitwith(fn {pair, _, _, _, _} -> pair in tuples end, impls)

    if overridable_impls != [] do
      :ets.insert(table, {{:elixir, :impls}, impls})

    case value do
      atom when is_atom(atom) ->
        {atom, 0}

      {atom, 0} = tuple when is_atom(atom) ->
        tuple

      other ->
        error_message =
          "expected the @on_load attribute to be an atom or a " <>
            "{atom, 0} tuple, got: #{inspect(other)}"

        raise ArgumentError, error_message
    end
  end

