code: def test_clear_called():
      a = nn.NdArray(1)
      assert a.clear_called == False
      a.fill(3)
      assert a.clear_called == False
      a.clear()
      assert a.clear_called == True
  
      a.fill(3)
      assert a.clear_called == False
      a.clear()
      assert a.clear_called == True
      a.zero()
      assert a.clear_called == False
      a.clear()
      assert a.clear_called == True
  
      a.data[0] = -1
      assert a.clear_called == False
  
imports: import numpy
  import nnabla
  import pytest
  from nnabla.ext_utils import get_extension_context
  import nnabla.functions
label_desc: Use image node_id 4 for calling a global function with example usage: test_clear_called() without return types