Perform a deep copy when copying pytrees

src/jaxsim/utils.py

@@ -96,7 +96,7 @@ def mutable(self: T, mutable: bool = True, validate: bool = False) -> T:
         return self
 
     def copy(self: T) -> T:
-        obj = jax.tree_util.tree_map(lambda leaf: leaf, self)
+        obj = copy.deepcopy(self)
         obj._set_mutability(mutability=self._mutability())
         return obj