code: def _draw_boundary_edges(
      ax,
      grid_points,
      grid_pred_as_matrix,
      boundary_marker,
      boundary_markersize,
      colors,
      w,
      h,
  ):
      ntiles = grid_pred_as_matrix.shape[0]
  
      # find transitions from one class to the other moving horizontally
      dx = np.diff(grid_pred_as_matrix, axis=1)
      dx = np.abs(dx)
      # put a zero col vector on the left to restore size
      dx = np.hstack([np.zeros((ntiles, 1)), dx])
  
      # find transitions moving vertically, bottom to top (grid matrix is flipped vertically btw)
      dy = np.diff(grid_pred_as_matrix, axis=0)
      dy = np.abs(dy)
      # put a zero row vector on the top to restore size
      dy = np.vstack([np.zeros((1, ntiles)), dy])
  
      dx_edge_idx = np.where(
          dx.reshape(-1)
      )  # what are the indexes of dx class transitions?
      dy_edge_idx = np.where(
          dy.reshape(-1)
      )  # what are the indexes of dy class transitions?
      dx_edges = grid_points[
          dx_edge_idx
      ]  # get v1,v2 coordinates of left-to-right transitions
      dy_edges = grid_points[
          dy_edge_idx
      ]  # get v1,v2 coordinates of bottom-to-top transitions
  
      # Plot the boundary markers in between tiles; e.g., shift dx stuff to the left half a tile
      ax.plot(
          dx_edges[:, 0] - w / 2,
          dx_edges[:, 1],
          boundary_marker,
          markersize=boundary_markersize,
          c=colors["class_boundary"],
          alpha=1.0,
      )
      ax.plot(
          dy_edges[:, 0],
          dy_edges[:, 1] - h / 2,
          boundary_marker,
          markersize=boundary_markersize,
          c=colors["class_boundary"],
          alpha=1.0,
      )
  
file_path: dtreeviz/dtreeviz/classifiers.py
imports: from typing import Tuple
  import matplotlib.pyplot
  import numpy
  import pandas
  from PIL import ImageColor
  from colour import Color
  from matplotlib import patches
  from matplotlib.collections import PatchCollection
  from dtreeviz import utils
  from dtreeviz.colors import adjust_colors
  from dtreeviz.utils import add_classifier_legend, _format_axes
label_desc: Use image node_id 6 for calling a global function with example usage: _draw_boundary_edges(ax, grid_points, grid_pred_as_matrix, boundary_marker, boundary_markersize, colors, w, h) without return types