code: def test_preallocation():
      dali.backend.PreallocateDeviceMemory(
          0, 0
      )  # initialize the context
      dali.backend.ReleaseUnusedMemory()
      mem_info = get_device_memory_info()
      if mem_info is None:
          raise SkipTest("Python bindings for NVML not found, skipping")
      free_before_prealloc = mem_info.free
      size = 256 << 20
      dali.backend.PreallocateDeviceMemory(size, 0)
      free_after_prealloc = get_device_memory_info().free
      assert (
          free_after_prealloc < free_before_prealloc
      )  # check that something was allocated
      dali.backend.ReleaseUnusedMemory()
      free_after_release = get_device_memory_info().free
      assert free_after_release > free_after_prealloc
  
imports: import numpy
  import nvidia.dali.fn
  import nvidia.dali.types
  import warnings
  from numpy.testing import assert_array_equal
  from nvidia.dali import pipeline_def
  from nvidia.dali.backend_impl import TensorCPU, TensorListCPU, TensorListGPU
  from nvidia.dali.backend_impl import types
  import nvidia.dali
  from nose_utils import assert_raises
  from nose import SkipTest
  from test_utils import dali_type_to_np, py_buffer_from_address, get_device_memory_info
label_desc: Use image node_id 1 for calling a global function with example usage: test_preallocation() without return types