Docserver: there is only one.

chrome/common/extensions/docs/server2/file_system.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import os
 
 class FileNotFoundError(Exception):
   def __init__(self, filename):
     Exception.__init__(self, filename)
 
@@ skipping 33 matching lines @@
   '''
   def Read(self, paths, binary=False):
     '''Reads each file in paths and returns a dictionary mapping the path to the
     contents. If a path in paths ends with a '/', it is assumed to be a
     directory, and a list of files in the directory is mapped to the path.
 
     If binary=False, the contents of each file will be unicode parsed as utf-8,
     and failing that as latin-1 (some extension docs use latin-1). If
     binary=True then the contents will be a str.
     '''
-    raise NotImplementedError()
+    raise NotImplementedError(self.__class__)
 
   def ReadSingle(self, path, binary=False):
     '''Reads a single file from the FileSystem.
     '''
     return self.Read([path], binary=binary).Get()[path]
 
   # TODO(cduvall): Allow Stat to take a list of paths like Read.
   def Stat(self, path):
     '''Returns a |StatInfo| object containing the version of |path|. If |path|
     is a directory, |StatInfo| will have the versions of all the children of
     the directory in |StatInfo.child_versions|.
     '''
-    raise NotImplementedError()
+    raise NotImplementedError(self.__class__)
 
   def GetIdentity(self):
     '''The identity of the file system, exposed for caching classes to
     namespace their caches. this will usually depend on the configuration of
     that file system - e.g. a LocalFileSystem with a base path of /var is
     different to that of a SubversionFileSystem with a base path of /bar, is
     different to a LocalFileSystem with a base path of /usr.
     '''
-    raise NotImplementedError()
+    raise NotImplementedError(self.__class__)