code: def validate(self, proposal):
      value = proposal["value"]
  
      if "index" in value:
          # We treat index special, so we might as well do some checking:
          idx = value["index"].array
          array = idx.array if isinstance(idx, NDArrayWidget) else idx
          if array.dtype.kind != "u":
              raise TraitError(
                  "Index attribute must have unsigned integer data"
              )
          if array.ndim != 1:
              raise TraitError(
                  "Index attribute must be a flat array. Consider using array.ravel()."
              )
  
      return value
  
file_path: pythreejs/pythreejs/core/BufferGeometry.py
imports: from ipywidgets import register, widget_serialization
  from traitlets import validate, TraitError, Undefined
  from ipydatawidgets import NDArrayWidget, get_union_array
  from .Geometry import _make_key_filter
  from .BufferGeometry_autogen import BufferGeometry
label_desc: Use image node_id 2 for calling the BufferGeometry obj's underlying member method code with example usage: obj.validate(proposal) and returns: value