code: def walk(top, topdown=True, onerror=None, followlinks=False):
      """Directory tree generator.
  
      For each directory in the directory tree rooted at top (including top
      itself, but excluding '.' and '..'), yields a 3-tuple
  
          dirpath, dirnames, filenames
  
      dirpath is a string, the path to the directory.  dirnames is a list of
      the names of the subdirectories in dirpath (including symlinks to directories,
      and excluding '.' and '..').
      filenames is a list of the names of the non-directory files in dirpath.
      Note that the names in the lists are just names, with no path components.
      To get a full path (which begins with top) to a file or directory in
      dirpath, do os.path.join(dirpath, name).
  
      If optional arg 'topdown' is true or not specified, the triple for a
      directory is generated before the triples for any of its subdirectories
      (directories are generated top down).  If topdown is false, the triple
      for a directory is generated after the triples for all of its
      subdirectories (directories are generated bottom up).
  
      When topdown is true, the caller can modify the dirnames list in-place
      (e.g., via del or slice assignment), and walk will only recurse into the
      subdirectories whose names remain in dirnames; this can be used to prune the
      search, or to impose a specific order of visiting.  Modifying dirnames when
      topdown is false has no effect on the behavior of os.walk(), since the
      directories in dirnames have already been generated by the time dirnames
      itself is generated. No matter the value of topdown, the list of
      subdirectories is retrieved before the tuples for the directory and its
      subdirectories are generated.
  
      By default errors from the os.scandir() call are ignored.  If
      optional arg 'onerror' is specified, it should be a function; it
      will be called with one argument, an OSError instance.  It can
      report the error to continue with the walk, or raise the exception
      to abort the walk.  Note that the filename is available as the
      filename attribute of the exception object.
  
      By default, os.walk does not follow symbolic links to subdirectories on
      systems that support them.  In order to get this functionality, set the
      optional argument 'followlinks' to true.
  
      Caution:  if you pass a relative pathname for top, don't change the
      current working directory between resumptions of walk.  walk never
      changes the current directory, and assumes that the client doesn't
      either.
  
      Example:
  
      import os
      from os.path import join, getsize
      for root, dirs, files in os.walk('python/Lib/email'):
          print(root, "consumes ")
          print(sum(getsize(join(root, name)) for name in files), end=" ")
          print("bytes in", len(files), "non-directory files")
          if 'CVS' in dirs:
              dirs.remove('CVS')  # don't visit CVS directories
  
      """
      sys.audit("os.walk", top, topdown, onerror, followlinks)
      return _walk(fspath(top), topdown, onerror, followlinks)
  
imports: import abc
  import sys
  import stat
  from _collections_abc import _check_methods
  from os.path import curdir, pardir, sep, pathsep, defpath, extsep, altsep, devnull
  from _collections_abc import MutableMapping, Mapping
label_desc: Use image node_id 6 for calling a global function with example usage: walk(top, topdown, onerror, followlinks) and returns: _walk