code: def initialise_grid_sampler(self):
      self.sampler = [
          [
              GridSampler(
                  reader=reader,
                  csv_reader=None,
                  window_sizes=self.data_param,
                  batch_size=self.net_param.batch_size,
                  spatial_window_size=self.action_param.spatial_window_size,
                  window_border=self.action_param.border,
                  smaller_final_batch_mode=self.net_param.smaller_final_batch_mode,
                  queue_length=self.net_param.queue_length,
              )
              for reader in self.readers
          ]
      ]
  
imports: import tensorflow
  from niftynet.application.base_application import BaseApplication
  from niftynet.engine.application_factory import ApplicationNetFactory, InitializerFactory, OptimiserFactory
  from niftynet.engine.application_variables import CONSOLE, NETWORK_OUTPUT, TF_SUMMARIES
  from niftynet.engine.sampler_grid_v2 import GridSampler
  from niftynet.engine.sampler_resize_v2 import ResizeSampler
  from niftynet.engine.sampler_uniform_v2 import UniformSampler
  from niftynet.engine.sampler_weighted_v2 import WeightedSampler
  from niftynet.engine.sampler_balanced_v2 import BalancedSampler
  from niftynet.engine.windows_aggregator_grid import GridSamplesAggregator
  from niftynet.engine.windows_aggregator_resize import ResizeSamplesAggregator
  from niftynet.io.image_reader import ImageReader
  from niftynet.layer.crop import CropLayer
  from niftynet.layer.histogram_normalisation import HistogramNormalisationLayer
  from niftynet.layer.loss_regression import LossFunction
  from niftynet.layer.mean_variance_normalisation import MeanVarNormalisationLayer
  from niftynet.layer.pad import PadLayer
  from niftynet.layer.post_processing import PostProcessingLayer
  from niftynet.layer.rand_flip import RandomFlipLayer
  from niftynet.layer.rand_rotation import RandomRotationLayer
  from niftynet.layer.rand_spatial_scaling import RandomSpatialScalingLayer
  from niftynet.layer.rgb_histogram_equilisation import RGBHistogramEquilisationLayer
  from niftynet.evaluation.regression_evaluator import RegressionEvaluator
  from niftynet.layer.rand_elastic_deform import RandomElasticDeformationLayer
  from niftynet.contrib.csv_reader.csv_reader import CSVReader
  from niftynet.contrib.csv_reader.sampler_resize_v2_csv import ResizeSamplerCSV
  from niftynet.contrib.csv_reader.sampler_grid_v2_csv import GridSamplerCSV
  from niftynet.contrib.csv_reader.sampler_uniform_v2_csv import UniformSamplerCSV
  from niftynet.contrib.csv_reader.sampler_weighted_v2_csv import WeightedSamplerCSV
  from niftynet.contrib.csv_reader.sampler_balanced_v2_csv import BalancedSamplerCSV
label_desc: Use image node_id 6 for calling the RegressionApplication obj's underlying member method code with example usage: obj.initialise_grid_sampler() without return types