DOC: show kinematic variable expressions (#497)

* MAINT: ignore stackexchange link
  https://github.com/ComPWA/tensorwaves/actions/runs/6273619138/job/17037692006

docs/amplitude-analysis.ipynb

@@ -558,7 +558,23 @@
     "\n",
     ":::\n",
     "\n",
-    "A problem is that {class}`.ParametrizedBackendFunction` takes a {obj}`.DataSample` with kinematic variables for the helicity formalism as input, not a set of four-momenta. We therefore need to construct a {class}`.DataTransformer` to transform these four-momenta to function variables. In this case, we work with the helicity formalism, so we construct a {class}`.SympyDataTransformer`:"
+    "A problem is that {class}`.ParametrizedBackendFunction` takes a {obj}`.DataSample` with kinematic variables for the helicity formalism as input, not a set of four-momenta. We therefore need to construct a {class}`.DataTransformer` to transform these four-momenta to function variables. In this case, we work with the helicity formalism, so we construct a {class}`.SympyDataTransformer`. This **numerical** data transformer is created from symbolic expressions, in this case, from expressions that relate four-momenta to helicity angles and invariant masses:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "jupyter": {
+     "source_hidden": true
+    },
+    "tags": [
+     "hide-input"
+    ]
+   },
+   "outputs": [],
+   "source": [
+    "Math(aslatex(model.kinematic_variables))"
    ]
   },
   {
@@ -2018,7 +2034,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.17"
+   "version": "3.8.18"
   }
  },
  "nbformat": 4,

docs/conf.py

@@ -339,6 +339,9 @@ def get_tensorflow_url() -> str:
     linkcheck_anchors_ignore = [
         r"pip\-installation\-gpu\-cuda",
     ]
+linkcheck_ignore = [
+    "https://unix.stackexchange.com/a/129144",
+]
 
 # Settings for myst_nb
 nb_execution_show_tb = True