code: def layerContentsValidator(value, ufoPathOrFileSystem):
      """
      Check the validity of layercontents.plist.
      Version 3+.
      """
      if isinstance(ufoPathOrFileSystem, fs.base.FS):
          fileSystem = ufoPathOrFileSystem
      else:
          fileSystem = fs.osfs.OSFS(ufoPathOrFileSystem)
  
      bogusFileMessage = (
          "layercontents.plist in not in the correct format."
      )
      # file isn't in the right format
      if not isinstance(value, list):
          return False, bogusFileMessage
      # work through each entry
      usedLayerNames = set()
      usedDirectories = set()
      contents = {}
      for entry in value:
          # layer entry in the incorrect format
          if not isinstance(entry, list):
              return False, bogusFileMessage
          if not len(entry) == 2:
              return False, bogusFileMessage
          for i in entry:
              if not isinstance(i, str):
                  return False, bogusFileMessage
          layerName, directoryName = entry
          # check directory naming
          if directoryName != "glyphs":
              if not directoryName.startswith("glyphs."):
                  return (
                      False,
                      "Invalid directory name (%s) in layercontents.plist."
                      % directoryName,
                  )
          if len(layerName) == 0:
              return False, "Empty layer name in layercontents.plist."
          # directory doesn't exist
          if not fileSystem.exists(directoryName):
              return (
                  False,
                  "A glyphset does not exist at %s." % directoryName,
              )
          # default layer name
          if (
              layerName == "public.default"
              and directoryName != "glyphs"
          ):
              return (
                  False,
                  "The name public.default is being used by a layer that is not the default.",
              )
          # check usage
          if layerName in usedLayerNames:
              return (
                  False,
                  "The layer name %s is used by more than one layer."
                  % layerName,
              )
          usedLayerNames.add(layerName)
          if directoryName in usedDirectories:
              return (
                  False,
                  "The directory %s is used by more than one layer."
                  % directoryName,
              )
          usedDirectories.add(directoryName)
          # store
          contents[layerName] = directoryName
      # missing default layer
      foundDefault = "glyphs" in contents.values()
      if not foundDefault:
          return (
              False,
              "The required default glyph set is not in the UFO.",
          )
      return True, None
  
imports: import calendar
  from io import open
  import fs.base
  import fs.osfs
  from collections.abc import Mapping
  from fontTools.ufoLib.utils import numberTypes
label_desc: Use image node_id 42 for calling a global function with example usage: layerContentsValidator(value, ufoPathOrFileSystem) and returns: True,  None, False,  bogusFileMessage, False,  str, False,  bogusFileMessage, False,  bogusFileMessage, False,  str, False,  unknown, False,  str, False,  unknown, False,  unknown, False,  bogusFileMessage, False,  unknown