     case Mix.Utils.parse_mfa(callee) do
       {:ok, mfa_list} ->
         mfa_list_length = length(mfa_list)
+
         fn {module, function, arity} ->
           mfa_list == Enum.take([module, function, arity], mfa_list_length)
         end
+
       :error ->
-        Mix.raise "xref callers CALLEE expects Module, Module.function, or Module.function/arity, " <>
-                  "got: " <> callee
+        Mix.raise(
+          "xref callers CALLEE expects Module, Module.function, or Module.function/arity, " <>
+            "got: " <> callee
+        )
     end
   end
 

    cond do
      excluded?(module, func, arity, excludes) ->
        nil
      skip?(module, func, arity) ->
        nil
      exports == :unknown_module ->
        {Enum.sort(lines), :unknown_module, module, func, arity, nil}
      is_atom(exports) and not function_exported?(module, func, arity) ->
        {Enum.sort(lines), :unknown_function, module, func, arity, nil}
      is_list(exports) and {func, arity} not in exports ->
        {Enum.sort(lines), :unknown_function, module, func, arity, exports}
      true ->
        nil
    end

  end

  defp message({_lines, :unknown_module, module, function, arity, _}) do
    [
      "function ",
      Exception.format_mfa(module, function, arity),
      " is undefined (module #{inspect(module)} is not available)"
    ]
  end

  defp format_file_lines(file, [line]) do
