Add tests for body.find_all() of joints and geoms, fix error message.

Fixes #2525

PiperOrigin-RevId: 742685596
Change-Id: I5f0969967f2490d32e5691983e8d0c363d48a6bd

python/mujoco/specs.cc

@@ -261,7 +261,7 @@ py::list FindAllImpl(raw::MjsBody& body, mjtObj objtype, bool recursive) {
         // this should never happen
         throw pybind11::value_error(
             "body.find_all supports the types: body, frame, geom, site, "
-            "light, camera.");
+            "joint, light, camera.");
         break;
     }
     el = mjs_nextChild(&body, el, recursive);

python/mujoco/specs_test.py

@@ -636,6 +636,8 @@ class SpecsTest(absltest.TestCase):
             <site name="site4"/>
             <body name="body4">
               <site name="site5"/>
+              <joint name="joint1"/>
+              <geom name="geom1" size="1"/>
             </body>
           </body>
         </body>
@@ -649,6 +651,8 @@ class SpecsTest(absltest.TestCase):
     self.assertLen(spec.sites, 5)
     self.assertLen(spec.worldbody.find_all('body'), 4)
     self.assertLen(spec.worldbody.find_all('site'), 5)
+    self.assertLen(spec.worldbody.find_all('joint'), 1)
+    self.assertLen(spec.worldbody.find_all('geom'), 1)
     self.assertEqual(spec.bodies[1].name, 'body1')
     self.assertEqual(spec.bodies[2].name, 'body2')
     self.assertEqual(spec.bodies[3].name, 'body3')