code: def test_locations(self):
      markers = marker_layer(self.locations)
      locations = [marker.location for marker in markers.markers]
      assert locations == self.locations
  
imports: import unittest
  import pytest
  import numpy
  import traitlets
  from ..marker import MarkerOptions, Marker, Markers, Symbol, marker_layer, symbol_layer
label_desc: Use image node_id 3 for calling the MarkerLayer obj's underlying member method code with example usage: obj.test_locations() without return types