code: def test_xavier(self, nn_init):
      callback = init.XavierNormal(gain=100)
      mock = MagicMock()
      callback.initialiser(mock)
      nn_init.xavier_normal_.assert_called_once_with(
          mock.weight.data, gain=100
      )
  
      callback = init.XavierUniform(gain=100)
      mock = MagicMock()
      callback.initialiser(mock)
      nn_init.xavier_uniform_.assert_called_once_with(
          mock.weight.data, gain=100
      )
  
file_path: torchbearer/tests/callbacks/test_init.py
imports: import torch
  from unittest import TestCase
  from mock import MagicMock, patch
  import torchbearer
  import torchbearer.callbacks.init
label_desc: Use image node_id 2 for calling the TestSimpleInits obj's underlying member method code with example usage: obj.test_xavier(nn_init) without return types