code: def test_overlay_gridspace_collate(self):
      grid = GridSpace(
          {
              (i, j): Curve(np.arange(10) * i)
              for i in range(3)
              for j in range(3)
          }
      )
      overlaid = Overlay([grid, grid, grid]).collate()
      self.assertEqual(overlaid, grid * grid * grid)
  
file_path: holoviews/holoviews/tests/core/test_collation.py
imports: import itertools
  import numpy
  from holoviews.core import Collator, GridSpace, HoloMap, NdOverlay, Overlay
  from holoviews.element import Curve
  from holoviews.element.comparison import ComparisonTestCase
label_desc: Use image node_id 9 for calling the TestCollation obj's underlying member method code with example usage: obj.test_overlay_gridspace_collate() without return types