message: ek.schedule support dict
diff: @@ -1320,6 +1320,9 @@ def schedule(*args):
  elif issubclass(t, tuple) or issubclass(t, list):
  for v in a:
  result |= schedule(v)
  + elif issubclass(t, _Mapping):
  + for k, v in a.items():
  + result |= schedule(v)
  return result
  