message: ek.set_label now works for enoki_structs in python
diff: @@ -1304,8 +1304,9 @@ def label(a):
  def set_label(a, label):
  if _ek.is_jit_array_v(a) or _ek.is_diff_array_v(a):
  a.set_label_(label)
  - else:
  - raise Exception("set_label(): only supported for JIT and AD arrays!")
  + elif _ek.is_enoki_struct_v(a):
  + for k in a.ENOKI_STRUCT.keys():
  + set_label(getattr(a, k), label + "_" + k)
  def schedule(*args):
  