class_docstr: Sort example gallery by title of subsection.
  
  Assumes README.txt exists for all subsections and uses the subsection with
  dashes, '---', as the adornment.
class_docstr_tok: ["Sort","example","gallery","by","title","of","subsection",".","Assumes","README.txt","exists","for","all","subsections","and","uses","the","subsection","with","dashes",",","'","--","-","'",",","as","the","adornment","."]
code: def __call__(self, directory):
      src_path = os.path.normpath(os.path.join(self.src_dir, directory))
  
      # Forces Release Highlights to the top
      if os.path.basename(src_path) == "release_highlights":
          return "0"
  
      readme = os.path.join(src_path, "README.txt")
  
      try:
          with open(readme, "r") as f:
              content = f.read()
      except FileNotFoundError:
          return directory
  
      title_match = self.regex.search(content)
      if title_match is not None:
          return title_match.group(1)
      return directory
  
imports: import os
  import re
  import sys
  import warnings
  from datetime import datetime
  from io import StringIO
  from pathlib import Path
  from sklearn.externals._packaging.version import parse
  import sphinx_gallery
  from github_link import make_linkcode_resolve
  from sphinx_gallery.notebook import add_code_cell, add_markdown_cell
  from sphinx_gallery.sorting import ExampleTitleSortKey
  import sklearn
  from sklearn.experimental import enable_iterative_imputer
  from sklearn.experimental import enable_halving_search_cv
  from sklearn.utils.fixes import VisibleDeprecationWarning
label_desc: Use image node_id 3 for calling the SubSectionTitleOrder obj's underlying member method code with example usage: obj.__call__(directory) and returns: directory, str, title_match, directory