diff --git a/IPython/nbformat/current.py b/IPython/nbformat/current.py
index 5f17051..8d5ed5d 100644
--- a/IPython/nbformat/current.py
+++ b/IPython/nbformat/current.py
@@ -35,7 +35,7 @@ from IPython.nbformat import v3 as _v_latest
 from .reader import reads as reader_reads
 from .reader import versions
 from .convert import convert
-from .validator import nbvalidate
+from .validator import validate
 
 #-----------------------------------------------------------------------------
 # Code
@@ -79,7 +79,7 @@ def parse_py(s, **kwargs):
 def reads_json(s, **kwargs):
     """Read a JSON notebook from a string and return the NotebookNode object."""
     nbjson = reader_reads(s)
-    num_errors = nbvalidate(nbjson)
+    num_errors = validate(nbjson)
     if num_errors > 0:
         print("Num errors: %d" % num_errors)
     return convert(nbjson, current_nbformat)
@@ -87,7 +87,7 @@ def reads_json(s, **kwargs):
 
 def writes_json(nb, **kwargs):
     nbjson = versions[current_nbformat].writes_json(nb, **kwargs)
-    num_errors = nbvalidate(nbjson)
+    num_errors = validate(nbjson)
     if num_errors > 0:
         print("Num errors: %d" % num_errors)
     return nbjson
diff --git a/IPython/nbformat/validator.py b/IPython/nbformat/validator.py
index 57d446b..a03a738 100644
--- a/IPython/nbformat/validator.py
+++ b/IPython/nbformat/validator.py
@@ -1,12 +1,10 @@
 from __future__ import print_function
 #!/usr/bin/env python
 # -*- coding: utf8 -*-
-import argparse
-import traceback
 import json
 import os
 
-from IPython.external.jsonschema import Draft3Validator, validate, ValidationError
+from IPython.external.jsonschema import Draft3Validator
 import IPython.external.jsonpointer as jsonpointer
 from IPython.utils.py3compat import iteritems
 
@@ -16,7 +14,7 @@ schema = os.path.join(
     os.path.split(__file__)[0], "v%d" % nbformat, nbformat_schema)
 
 
-def nbvalidate(nbjson, key='/', verbose=True):
+def validate(nbjson, key='/', verbose=True):
     v3schema = resolve_ref(json.load(open(schema, 'r')))
     if key:
         v3schema = jsonpointer.resolve_pointer(v3schema, key)
@@ -34,31 +32,33 @@ def resolve_ref(json, base=None):
 
     only support local reference to the same json
     """
-    if not base :
+    if not base:
         base = json
 
     temp = None
     if type(json) is list:
-        temp = [];
+        temp = []
         for item in json:
             temp.append(resolve_ref(item, base=base))
     elif type(json) is dict:
-        temp = {};
-        for key,value in iteritems(json):
+        temp = {}
+        for key, value in iteritems(json):
             if key == '$ref':
-                return resolve_ref(jsonpointer.resolve_pointer(base,value), base=base)
-            else :
-                temp[key]=resolve_ref(value, base=base)
-    else :
+                return resolve_ref(
+                    jsonpointer.resolve_pointer(base, value), base=base)
+            else:
+                temp[key] = resolve_ref(value, base=base)
+    else:
         return json
     return temp
 
+
 def convert(namein, nameout, indent=2):
     """resolve the references of namein, save the result in nameout"""
     jsn = None
-    with open(namein) as file :
+    with open(namein) as file:
         jsn = json.load(file)
     v = resolve_ref(jsn, base=jsn)
     x = jsonpointer.resolve_pointer(v, '/notebook')
-    with open(nameout,'w') as file:
-        json.dump(x,file,indent=indent)
+    with open(nameout, 'w') as file:
+        json.dump(x, file, indent=indent)