Add spec.find_site().

PiperOrigin-RevId: 702733068
Change-Id: I4cc7fd2b9b59185a4458fdac8537f8287af1f295

python/mujoco/specs.cc

@@ -344,6 +344,12 @@ PYBIND11_MODULE(_specs, m) {
         return mjs_findFrame(self.ptr, name.c_str());
       },
       py::return_value_policy::reference_internal);
+  mjSpec.def(
+      "find_site",
+      [](MjSpec& self, std::string& name) -> raw::MjsSite* {
+        return mjs_asSite(mjs_findElement(self.ptr, mjOBJ_SITE, name.c_str()));
+      },
+      py::return_value_policy::reference_internal);
   mjSpec.def(
       "find_default",
       [](MjSpec& self, std::string& classname) -> const raw::MjsDefault* {

python/mujoco/specs_test.py

@@ -723,6 +723,7 @@ class SpecsTest(absltest.TestCase):
     self.assertIsNotNone(head)
     site = head.first_site()
     self.assertIsNotNone(site)
+    self.assertEqual(site, spec.find_site('head'))
 
     site.delete()
     spec.sensors[-1].delete()