code: def test_autocast_rnn(self):
      if (
          torch.backends.mkldnn.is_available()
          and torch.ops.mkldnn._is_mkldnn_bf16_supported()
      ):
          x = torch.randn(1, 2, 1)
          hx = torch.randn(2, 2, 1)
          cx = torch.randn(2, 2, 1)
  
          m = torch.nn.LSTM(1, 1, 2).to(torch.bfloat16)
  
          # Raise ValueError when autocast is not enabled
          with self.assertRaisesRegex(
              ValueError, "input must have the type"
          ):
              m(x, (hx, cx))
  
          # Should be able to run the below case with autocast
          with torch.cpu.amp.autocast():
              m(x, (hx, cx))
  
imports: import collections
  import unittest
  import torch
  from torch.testing._internal.common_utils import TestCase, run_tests, IS_WINDOWS, skipIfTorchDynamo
  from torch.testing._internal.autocast_test_lists import AutocastCPUTestLists
  from torch.utils._python_dispatch import TorchDispatchMode
label_desc: Use image node_id 12 for calling the TestAutocastCPU obj's underlying member method code with example usage: obj.test_autocast_rnn() without return types