code: def GetFileEntryByPathSpec(self, path_spec):
      
      if not self.FileEntryExistsByPathSpec(path_spec):
        return None
      return os_file_entry.OSFileEntry(self._resolver_context, self, path_spec)
docs: Retrieves a file entry for a path specification.
  
      Args:
        path_spec (PathSpec): a path specification.
  
      Returns:
        OSFileEntry: a file entry or None if not available.