code: def _update_trie(self, dirname: str, trie: Trie) -> None:
      key = self._get_key(dirname)
      old_pattern = trie.longest_prefix(key).value
      matches = old_pattern.matches(
          dirname, DvcIgnore.DVCIGNORE_FILE, False
      )
  
      path = self.fs.join(dirname, DvcIgnore.DVCIGNORE_FILE)
      if not matches and self.fs.exists(path):
          name = self.fs.relpath(path, self.root_dir)
          new_pattern = DvcIgnorePatterns.from_file(path, self.fs, name)
          if old_pattern:
              plist, prefix = merge_patterns(
                  self.fs.flavour,
                  old_pattern.pattern_list,
                  old_pattern.dirname,
                  new_pattern.pattern_list,
                  new_pattern.dirname,
              )
              trie[key] = DvcIgnorePatterns(plist, prefix, self.fs.sep)
          else:
              trie[key] = new_pattern
      elif old_pattern:
          trie[key] = old_pattern
  
imports: import os
  import re
  from collections import namedtuple
  from itertools import chain, groupby, takewhile
  from typing import TYPE_CHECKING, List, Optional
  from pathspec.patterns import GitWildMatchPattern
  from pathspec.util import normalize_file
  from pygtrie import Trie
  from dvc.fs import Schemes, localfs
  from dvc.log import logger
  from dvc.pathspec_math import PatternInfo, merge_patterns
label_desc: Use image node_id 3 for calling the DvcIgnoreFilter obj's underlying member method code with example usage: obj._update_trie(dirname, trie) without return types