diff --git a/setup.py b/setup.py
index 65d2c69..64fa7d7 100755
--- a/setup.py
+++ b/setup.py
@@ -6,7 +6,7 @@
 
 setup(
     name="streamz_ext",
-    version='0.2.1',
+    version="0.2.1",
     description="Streams",
     url="http://github.com/xpdAcq/streamz_ext/",
     maintainer="Christopher J. Wright",
diff --git a/streamz_ext/parallel.py b/streamz_ext/parallel.py
index e161921..ac612ac 100644
--- a/streamz_ext/parallel.py
+++ b/streamz_ext/parallel.py
@@ -15,7 +15,7 @@
 
 from collections import Sequence
 
-NULL_COMPUTE = '~~NULL_COMPUTE~~'
+NULL_COMPUTE = "~~NULL_COMPUTE~~"
 
 
 def return_null(func):
@@ -33,8 +33,9 @@ def inner(x, *args, **kwargs):
 def filter_null_wrapper(func):
     @wraps(func)
     def inner(*args, **kwargs):
-        if (any(a == NULL_COMPUTE for a in args)
-                or any(v == NULL_COMPUTE for v in kwargs.values())):
+        if any(a == NULL_COMPUTE for a in args) or any(
+            v == NULL_COMPUTE for v in kwargs.values()
+        ):
             return NULL_COMPUTE
         else:
             return func(*args, **kwargs)
@@ -144,8 +145,13 @@ class gather(ParallelStream):
     def update(self, x, who=None):
         client = self.default_client()
         result = yield client.gather(x, asynchronous=True)
-        if not ((isinstance(result, Sequence) and any(
-                r == NULL_COMPUTE for r in result)) or result == NULL_COMPUTE):
+        if not (
+            (
+                isinstance(result, Sequence)
+                and any(r == NULL_COMPUTE for r in result)
+            )
+            or result == NULL_COMPUTE
+        ):
             result2 = yield self._emit(result)
             raise gen.Return(result2)
 
@@ -168,12 +174,12 @@ def update(self, x, who=None):
 @ParallelStream.register_api()
 class accumulate(ParallelStream):
     def __init__(
-            self,
-            upstream,
-            func,
-            start=core.no_default,
-            returns_state=False,
-            **kwargs
+        self,
+        upstream,
+        func,
+        start=core.no_default,
+        returns_state=False,
+        **kwargs
     ):
         self.func = filter_null_wrapper(func)
         self.state = start
diff --git a/test/test_parallel.py b/test/test_parallel.py
index cf49024..d6be14a 100644
--- a/test/test_parallel.py
+++ b/test/test_parallel.py
@@ -71,9 +71,9 @@ def f(acc, i):
 
     L = (
         scatter(source, backend=backend)
-            .scan(f, returns_state=True)
-            .gather()
-            .sink_to_list()
+        .scan(f, returns_state=True)
+        .gather()
+        .sink_to_list()
     )
     for i in range(3):
         yield source.emit(i)
@@ -141,10 +141,10 @@ def test_buffer(backend):
     source = Stream(asynchronous=True)
     L = (
         source.scatter(backend=backend)
-            .map(slowinc, delay=0.5)
-            .buffer(5)
-            .gather()
-            .sink_to_list()
+        .map(slowinc, delay=0.5)
+        .buffer(5)
+        .gather()
+        .sink_to_list()
     )
 
     start = time.time()
@@ -186,7 +186,9 @@ def test_filter(backend):
 @gen_test()
 def test_filter_map(backend):
     source = Stream(asynchronous=True)
-    futures = scatter(source, backend=backend).filter(lambda x: x % 2 == 0).map(inc)
+    futures = (
+        scatter(source, backend=backend).filter(lambda x: x % 2 == 0).map(inc)
+    )
     futures_L = futures.sink_to_list()
     L = futures.gather().sink_to_list()
 
diff --git a/test/test_parallel_dask.py b/test/test_parallel_dask.py
index 868896a..5ff7c1b 100644
--- a/test/test_parallel_dask.py
+++ b/test/test_parallel_dask.py
@@ -117,10 +117,10 @@ def test_buffer(c, s, a, b):
     source = Stream(asynchronous=True)
     L = (
         source.scatter()
-            .map(slowinc, delay=0.5)
-            .buffer(5)
-            .gather()
-            .sink_to_list()
+        .map(slowinc, delay=0.5)
+        .buffer(5)
+        .gather()
+        .sink_to_list()
     )
 
     start = time.time()
@@ -211,8 +211,7 @@ def test_filter(c, s, a, b):
 @gen_cluster(client=True)
 def test_filter_map(c, s, a, b):
     source = Stream(asynchronous=True)
-    futures = scatter(source).filter(
-        lambda x: x % 2 == 0).map(inc)
+    futures = scatter(source).filter(lambda x: x % 2 == 0).map(inc)
     futures_L = futures.sink_to_list()
     L = futures.gather().sink_to_list()