code: def calculate_one_cvert(self, u, v):
      vert = self.verts[u][v]
      return self.color(
          vert[0], vert[1], vert[2], self.u_set[u], self.v_set[v]
      )
  
file_path: sympy/sympy/plotting/pygletplot/plot_surface.py
imports: import pyglet.gl
  from sympy.core import S
  from sympy.plotting.pygletplot.plot_mode_base import PlotModeBase
label_desc: Use image node_id 3 for calling the PlotSurface obj's underlying member method code with example usage: obj.calculate_one_cvert(u, v) and returns: self