refactor: remove physics module (#299)

* fix: rename test_interfaces.py

Author: redeboer

docs/usage/step3.ipynb

@@ -627,7 +627,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Just like in {ref}`usage/step2:2.2 Generate intensity-based sample`, these _intensity components_ can each be expressed in a computational backend. This can be done with the helper function {func}`.create_intensity_component`. After that we, update the parameters with the optimized parameter values we found in {ref}`usage/step3:Perform fit`. The two components in the example below should be the same:"
+    "Just like in {ref}`usage/step2:2.2 Generate intensity-based sample`, these _intensity components_ can each be expressed in a computational backend. This can be done with the method {meth}`~ampform.helicity.HelicityModel.sum_components` from the original model and creating a new {class}`.LambdifiedFunction` from that expression. After that we, update the parameters with the optimized parameter values we found in {ref}`usage/step3:Perform fit`. The two components in the example below should be the same:"
    ]
   },
   {
@@ -636,17 +636,20 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "from tensorwaves.physics import create_intensity_component\n",
-    "\n",
-    "from_amplitudes = create_intensity_component(\n",
-    "    model,\n",
+    "added_components = model.sum_components(\n",
     "    components=[\n",
     "        R\"A_{J/\\psi(1S)_{+1} \\to f_{0}(500)_{0} \\gamma_{+1}; f_{0}(500)_{0} \\to \\pi^{0}_{0} \\pi^{0}_{0}}\",\n",
     "        R\"A_{J/\\psi(1S)_{+1} \\to f_{0}(980)_{0} \\gamma_{+1}; f_{0}(980)_{0} \\to \\pi^{0}_{0} \\pi^{0}_{0}}\",\n",
     "        R\"A_{J/\\psi(1S)_{+1} \\to f_{0}(1370)_{0} \\gamma_{+1}; f_{0}(1370)_{0} \\to \\pi^{0}_{0} \\pi^{0}_{0}}\",\n",
     "        R\"A_{J/\\psi(1S)_{+1} \\to f_{0}(1500)_{0} \\gamma_{+1}; f_{0}(1500)_{0} \\to \\pi^{0}_{0} \\pi^{0}_{0}}\",\n",
     "        R\"A_{J/\\psi(1S)_{+1} \\to f_{0}(1710)_{0} \\gamma_{+1}; f_{0}(1710)_{0} \\to \\pi^{0}_{0} \\pi^{0}_{0}}\",\n",
-    "    ],\n",
+    "    ]\n",
+    ")\n",
+    "from_amplitudes = LambdifiedFunction(\n",
+    "    model=SympyModel(\n",
+    "        expression=added_components,\n",
+    "        parameters=model.parameter_defaults,\n",
+    "    ),\n",
     "    backend=\"numpy\",\n",
     ")\n",
     "from_amplitudes.update_parameters(latest_parameters)"
@@ -658,9 +661,14 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "from_intensity = create_intensity_component(\n",
-    "    model,\n",
-    "    components=R\"I_{J/\\psi(1S)_{+1} \\to \\gamma_{+1} \\pi^{0}_{0} \\pi^{0}_{0}}\",\n",
+    "added_components = model.sum_components(\n",
+    "    components=[R\"I_{J/\\psi(1S)_{+1} \\to \\gamma_{+1} \\pi^{0}_{0} \\pi^{0}_{0}}\"]\n",
+    ")\n",
+    "from_intensity = LambdifiedFunction(\n",
+    "    model=SympyModel(\n",
+    "        expression=added_components,\n",
+    "        parameters=model.parameter_defaults,\n",
+    "    ),\n",
     "    backend=\"numpy\",\n",
     ")\n",
     "from_intensity.update_parameters(latest_parameters)"
@@ -747,7 +755,13 @@
     "logging.basicConfig()\n",
     "logging.getLogger().setLevel(logging.ERROR)\n",
     "intensity_components = [\n",
-    "    create_intensity_component(model, c, backend=\"numpy\")\n",
+    "    LambdifiedFunction(\n",
+    "        SympyModel(\n",
+    "            expression=model.sum_components([c]),\n",
+    "            parameters=model.parameter_defaults,\n",
+    "        ),\n",
+    "        backend=\"numpy\",\n",
+    "    )\n",
     "    for c in model.components\n",
     "    if c.startswith(\"I\")\n",
     "]\n",