code: def _process_vertices(self, element):
      style = self.style[self.cyclic_index]
      edge_color = style.get("edge_color")
      if edge_color not in element.nodes:
          edge_color = self.edge_color_index
      simplex_dim = element.get_dimension(edge_color)
      vertex_dim = element.nodes.get_dimension(edge_color)
      if vertex_dim and not simplex_dim:
          simplices = element.array([0, 1, 2])
          z = element.nodes.dimension_values(vertex_dim)
          z = z[simplices].mean(axis=1)
          element = element.add_dimension(
              vertex_dim, len(element.vdims), z, vdim=True
          )
      element._initialize_edgepaths()
      return element
  
imports: from collections import defaultdict
  import numpy
  import param
  from bokeh.models import Bezier, ColumnDataSource, EdgesAndLinkedNodes, NodesAndLinkedEdges, NodesOnly, Patches, StaticLayoutProvider
  from ...core.data import Dataset
  from ...core.options import Cycle, abbreviated_exception
  from ...core.util import dimension_sanitizer, unique_array
  from ...util.transform import dim
  from ..mixins import ChordMixin, GraphMixin
  from ..util import get_directed_graph_paths, process_cmap
  from .chart import ColorbarPlot, PointPlot
  from .element import CompositeElementPlot, LegendPlot
  from .styles import base_properties, fill_properties, line_properties, rgba_tuple, text_properties
label_desc: Use image node_id 1 for calling the TriMeshPlot obj's underlying member method code with example usage: obj._process_vertices(element) and returns: element