class_docstr: Helper class to check whether the plotter's rendered content has changed
  since the last call.
class_docstr_tok: ["Helper","class","to","check","whether","the","plotter","'s","rendered","content","has","changed","since","the","last","call","."]
code: def __call__(self):
      cur = self._capture()
      changed = pv.compare_images(self._prev, cur) > 0
      self._prev = cur
      return changed
  
imports: import itertools
  import platform
  import weakref
  import numpy
  import pytest
  from vtkmodules.vtkRenderingContext2D import vtkPen
  import pyvista
  from pyvista import examples
  from pyvista.plotting import charts
  from pyvista.plotting.colors import COLOR_SCHEMES
label_desc: Use image node_id 3 for calling the PlotterChanged obj's underlying member method code with example usage: obj.__call__() and returns: changed