code: def test_dtensor_dtype_conversion(self):
      device_mesh = DeviceMesh(
          self.device_type, list(range(self.world_size))
      )
      shard_spec = [Shard(0)]
      # by default we start from bf16 dtype
      local_tenor = torch.randn(2, 8, dtype=torch.bfloat16)
      bf16_sharded_dtensor = DTensor.from_local(
          local_tenor, device_mesh, shard_spec
      )
      self.assertEqual(bf16_sharded_dtensor.dtype, torch.bfloat16)
      self.assertEqual(
          bf16_sharded_dtensor.to_local().dtype, torch.bfloat16
      )
  
      # convert to float dtype
      fp32_sharded_dtensor = bf16_sharded_dtensor.float()
      self.assertEqual(fp32_sharded_dtensor.dtype, torch.float32)
      self.assertEqual(
          fp32_sharded_dtensor.to_local().dtype, torch.float32
      )
  
      # convert back to bf16 dtype
      bf16_sharded_dtensor1 = fp32_sharded_dtensor.type_as(
          bf16_sharded_dtensor
      )
      self.assertEqual(bf16_sharded_dtensor1.dtype, torch.bfloat16)
      self.assertEqual(
          bf16_sharded_dtensor1.to_local().dtype, torch.bfloat16
      )
  
      from torch.distributed._tensor.debug import (
          get_sharding_prop_cache_info,
      )
  
      # by this point we only have cache misses
      hits, misses, _, _ = get_sharding_prop_cache_info()
      self.assertEqual(hits, 0)
      self.assertEqual(misses, 2)
  
      # convert to fp32 again and see if there's cache hit
      fp32_sharded_dtensor1 = bf16_sharded_dtensor1.float()
      hits, misses, _, _ = get_sharding_prop_cache_info()
      # by now we should have cache hit
      self.assertEqual(hits, 1)
      self.assertEqual(misses, 2)
  
imports: import torch
  from torch.distributed._tensor import DeviceMesh, distribute_tensor, DTensor
  from torch.distributed._tensor.placement_types import _Partial, Replicate, Shard
  from torch.testing._internal.common_utils import run_tests
  from torch.testing._internal.distributed._tensor.common_dtensor import DTensorConverter, DTensorTestBase, with_comms
label_desc: Use image node_id 20 for calling the DistTensorOpsTest obj's underlying member method code with example usage: obj.test_dtensor_dtype_conversion() without return types