code: def test_no_locations(self):
      with self.assertRaises(traitlets.TraitError):
          heatmap_layer([])
  
imports: import unittest
  import pytest
  import traitlets
  from ..heatmap import _HeatmapOptionsMixin, heatmap_layer, Heatmap, WeightedHeatmap
  from ..geotraitlets import InvalidPointException, InvalidWeightException
label_desc: Use image node_id 14 for calling the HeatmapLayer obj's underlying member method code with example usage: obj.test_no_locations() without return types