code: def test_learning_rate_decay_factor() -> None:
      assert_valid_param(
          param_name="learning_rate_decay_factor",
          param_values=[0.1, 1e-10, 0.5, 1 - 1e-10],
      )
      assert_invalid_param(
          param_name="learning_rate_decay_factor",
          param_values=[
              -2,
              -1e-10,
              +1,
              +5,
              float("inf"),
              float("nan"),
              0,
          ],
          exp_msg="The value of `learning_rate_decay_factor` should be in the (0, 1) range (type=value_error)",
      )
  
file_path: gluonts/test/mx/trainer/test_trainer.py
imports: from typing import Any, List
  import pytest
  from gluonts.mx.trainer import Trainer
label_desc: Use image node_id 4 for calling a global function with example usage: test_learning_rate_decay_factor() without return types