message: Avoid triggering Python->C++ parameter conversion of empty iterables.
diff: @@ -165,7 +165,7 @@ class ParameterServer(Params):
  or isinstance(value,bool):
  return True
  # list float
  - elif all(isinstance(el, float) for el in value):
  + elif isinstance(value, list) and all(isinstance(el, float) for el in value):
  return True
  # list list float
  elif isinstance(value, list):
  