code: def test_trimesh_op_edge_color_categorical(self):
      edges = [(0, 1, 2, "A"), (1, 2, 3, "B")]
      nodes = [(-1, -1, 0), (0, 0, 1), (0, 1, 2), (1, 0, 3)]
      trimesh = TriMesh((edges, nodes), vdims="color").opts(
          edge_color="color"
      )
      plot = bokeh_renderer.get_plot(trimesh)
      cds = plot.handles["multi_line_1_source"]
      glyph = plot.handles["multi_line_1_glyph"]
      cmapper = plot.handles["edge_color_color_mapper"]
      self.assertEqual(
          property_to_dict(glyph.line_color),
          {"field": "edge_color", "transform": cmapper},
      )
      self.assertEqual(cds.data["edge_color"], np.array(["A", "B"]))
      self.assertEqual(cmapper.factors, ["A", "B"])
  
imports: import numpy
  from bokeh.models import EdgesAndLinkedNodes, NodesAndLinkedEdges, NodesOnly, Patches
  from bokeh.models.mappers import CategoricalColorMapper, LinearColorMapper
  from holoviews.core.data import Dataset
  from holoviews.element import Chord, Graph, Nodes, TriMesh, VLine, circular_layout
  from holoviews.plotting.bokeh.util import property_to_dict
  from holoviews.util.transform import dim
  from .test_plot import TestBokehPlot, bokeh_renderer
label_desc: Use image node_id 16 for calling the TestBokehTriMeshPlot obj's underlying member method code with example usage: obj.test_trimesh_op_edge_color_categorical() without return types