code: def test_once_per_epoch_lambda(self):
      @callbacks.once_per_epoch
      @callbacks.on_step_validation
      def callback_func(state):
          state["value"] += 1
  
      state = {torchbearer.EPOCH: 0, "value": 0}
  
      cb = callback_func
  
      cb.on_step_validation(state)
      self.assertTrue(state["value"] == 1)
  
      cb.on_step_validation(state)
      self.assertTrue(state["value"] == 1)
  
      state[torchbearer.EPOCH] += 1
      cb.on_step_validation(state)
      self.assertTrue(state["value"] == 2)
  
imports: import unittest
  import torchbearer.callbacks
  import torchbearer
label_desc: Use image node_id 27 for calling the TestDecorators obj's underlying member method code with example usage: obj.test_once_per_epoch_lambda() without return types