code: def test_collate_layout_hmap(self):
      layout = self.nested_overlay + self.nested_overlay
      collated = Collator(kdims=["delta"], merge_type=NdOverlay)
      for k, v in self.nesting_hmap.groupby(["delta"]).items():
          collated[k] = v + v
      collated = collated()
      self.assertEqual(repr(collated), repr(layout))
      self.assertEqual(collated.dimensions(), layout.dimensions())
  
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 7 for calling the TestCollation obj's underlying member method code with example usage: obj.test_collate_layout_hmap() without return types