code: def test_once_filter(self):
      # once = 10
      @Filter(once=10)
      def _fn(data):
          return data
  
      _res = []
      for i in range(100):
          cu_res = _fn(i)
          if cu_res is not None:
              _res.append(cu_res)
      assert _res == [9]
  
file_path: fastNLP/tests/core/callbacks/test_callback_event.py
imports: import pytest
  from functools import reduce
  from fastNLP.core.callbacks.callback_event import Event, Filter
label_desc: Use image node_id 2 for calling the TestFilter obj's underlying member method code with example usage: obj.test_once_filter() and returns: data