code: def decoder_slice_pipe(decoder_op, file_root, device, use_fast_idct):
      encoded, _ = fn.readers.file(file_root=file_root)
      start = types.Constant(np.array([0.0, 0.0]))
      end = types.Constant(np.array([0.5, 0.5]))
      decoded = decoder_op(
          encoded,
          start,
          end,
          device=device,
          output_type=types.RGB,
          use_fast_idct=use_fast_idct,
      )
      return decoded
  
imports: import glob
  import math
  import numpy
  import nvidia.dali.backend
  import nvidia.dali.fn
  import nvidia.dali.types
  import os
  import random
  from nvidia.dali import pipeline_def
  from nose2.tools import params
  from nose_utils import assert_raises
  from test_utils import check_output_pattern
  from test_utils import compare_pipelines
  from test_utils import get_dali_extra_path
  from test_utils import to_array
label_desc: Use image node_id 23 for calling a global function with example usage: decoder_slice_pipe(decoder_op, file_root, device, use_fast_idct) and returns: decoded