code: def initialise_sampler(self):
      self.sampler = [
          [
              RandomVectorSampler(
                  names=("vectors",),
                  vector_size=(self.toy_param.vector_size,),
                  batch_size=self.net_param.batch_size,
                  repeat=None,
                  mean=self.toy_param.mean,
                  stddev=self.toy_param.stddev,
              )
          ]
      ]
  
imports: from __future__ import absolute_import, print_function
  import tensorflow
  from niftynet.application.base_application import BaseApplication
  from niftynet.engine.application_factory import ApplicationNetFactory
  from niftynet.engine.application_factory import OptimiserFactory
  from niftynet.engine.application_variables import CONSOLE
  from niftynet.engine.application_variables import TF_SUMMARIES
  from niftynet.engine.sampler_random_vector_v2 import RandomVectorSampler
  from niftynet.layer.convolution import ConvolutionalLayer
  from niftynet.layer.fully_connected import FullyConnectedLayer
  from niftynet.network.base_net import BaseNet
label_desc: Use image node_id 3 for calling the ToyApplication obj's underlying member method code with example usage: obj.initialise_sampler() without return types