class_docstr: An NdOverlay allows a group of NdOverlay to be overlaid together. NdOverlay can
  be indexed out of an overlay and an overlay is an iterable that iterates
  over the contained layers.
code: def __init__(self, overlays=None, kdims=None, **params):
      super().__init__(overlays, kdims=kdims, **params)
  
imports: from functools import reduce
  import numpy
  import param
  from .dimension import Dimension, Dimensioned, ViewableElement, ViewableTree
  from .layout import AdjointLayout, Composable, Layout, Layoutable
  from .ndmapping import UniformNdMapping
  from .util import dimensioned_streams, sanitize_identifier, unique_array
label_desc: Use image node_id 1 to create a new NdOverlay object from inherited base classes: Overlayable, UniformNdMapping, CompositeOverlay with example: obj = NdOverlay(overlays, kdims)