modernize some Python code

Since we now require Python 3.6, we can use f-strings instead of
format() to make the code more readable.

* doc/org/tut01.org, doc/org/tut02.org, doc/org/tut03.org,
doc/org/tut21.org, doc/org/tut24.org, doc/org/tut90.org,
python/spot/__init__.py, python/spot/jupyter.py, tests/python/acc.py,
tests/python/acc_cond.ipynb, tests/python/complement_semidet.py,
tests/python/decompose.ipynb, tests/python/formulas.ipynb,
tests/python/highlighting.ipynb, tests/python/ipnbdoctest.py,
tests/python/ltlf.py, tests/python/parity.ipynb,
tests/python/product.ipynb, tests/python/relabel.py,
tests/python/satmin.ipynb, tests/python/stutter-inv.ipynb,
tests/python/twagraph-internals.ipynb, tests/python/zlktree.ipynb: Use
f-strings.

tests/python/acc_cond.ipynb

@@ -11,7 +11,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -100,7 +99,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -131,7 +129,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -194,7 +191,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -220,7 +216,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -252,7 +247,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -280,7 +274,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -331,7 +324,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -359,7 +351,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -400,7 +391,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -428,7 +418,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -455,7 +444,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -483,7 +471,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -552,7 +539,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -603,7 +589,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -630,7 +615,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -743,7 +727,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -775,11 +758,10 @@
     "acc = spot.acc_code('Fin(0) & Inf(1) | Inf(2)')\n",
     "print(\"acc =\", acc)\n",
     "for x in ([0, 1, 2], [1, 2], [0, 1], [0, 2], [0], [1], [2], []):\n",
-    "    print(\"acc.accepting({}) = {}\".format(x, acc.accepting(x)))"
+    "    print(f\"acc.accepting({x}) = {acc.accepting(x)}\")"
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -809,7 +791,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -837,7 +818,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -873,7 +853,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -909,7 +888,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -978,7 +956,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1049,7 +1026,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1078,7 +1054,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1108,7 +1083,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1138,7 +1112,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1170,7 +1143,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1202,7 +1174,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1235,7 +1206,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1264,7 +1234,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1292,7 +1261,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1320,7 +1288,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1346,11 +1313,10 @@
    "source": [
     "print(\"acc =\", acc)\n",
     "for x in ([0, 1, 2, 3, 10], [1, 2]):\n",
-    "    print(\"acc.accepting({}) = {}\".format(x, acc.accepting(x)))"
+    "    print(f\"acc.accepting({x}) = {acc.accepting(x)}\")"
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1419,7 +1385,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1446,7 +1411,6 @@
    ]
   },
   {
-   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
@@ -1566,7 +1530,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.5"
+   "version": "3.11.8"
   }
  },
  "nbformat": 4,