code: def test_invalidate(self):
      try:
          import numpy as np
      except ImportError:
          pytest.skip("numpy not available")
  
      a = np.zeros((1, 1))
      p = pyvips.Image.new_from_memory(a.data, 1, 1, 1, "double")
      v = p(0, 0)
      assert v == [0]
      a[0, 0] = 1
      v = p(0, 0)
      assert v == [0]
      p.invalidate()
      v = p(0, 0)
      assert v == [1]
  
file_path: pyvips/tests/test_image.py
imports: import pyvips
  import pytest
  from helpers import JPEG_FILE
label_desc: Use image node_id 5 for calling the TestImage obj's underlying member method code with example usage: obj.test_invalidate() without return types