diff --git a/ffmpeg/__init__.py b/ffmpeg/__init__.py
index 7e913d37..a88d344d 100644
--- a/ffmpeg/__init__.py
+++ b/ffmpeg/__init__.py
@@ -1,10 +1,22 @@
 from __future__ import unicode_literals
-
-from . import _filters, _ffmpeg, _run, _probe
-from ._filters import *
+from . import nodes
+from . import _ffmpeg
+from . import _filters
+from . import _probe
+from . import _run
+from . import _view
+from .nodes import *
 from ._ffmpeg import *
+from ._filters import *
+from ._probe import *
 from ._run import *
 from ._view import *
-from ._probe import *
 
-__all__ = _filters.__all__ + _ffmpeg.__all__ + _run.__all__ + _view.__all__ + _probe.__all__
+__all__ = (
+    nodes.__all__
+    + _ffmpeg.__all__
+    + _probe.__all__
+    + _run.__all__
+    + _view.__all__
+    + _filters.__all__
+)
diff --git a/ffmpeg/_filters.py b/ffmpeg/_filters.py
index 2cbdb362..cc550bfc 100644
--- a/ffmpeg/_filters.py
+++ b/ffmpeg/_filters.py
@@ -8,7 +8,7 @@
 def filter_multi_output(stream_spec, filter_name, *args, **kwargs):
     """Apply custom filter with one or more outputs.
 
-    This is the same as ``filter_`` except that the filter can produce more than one output.
+    This is the same as ``filter`` except that the filter can produce more than one output.
 
     To reference an output stream, use either the ``.stream`` operator or bracket shorthand:
 
diff --git a/ffmpeg/nodes.py b/ffmpeg/nodes.py
index d558e223..34d1e44a 100644
--- a/ffmpeg/nodes.py
+++ b/ffmpeg/nodes.py
@@ -336,3 +336,8 @@ def filter_operator(name=None):
 
 def output_operator(name=None):
     return stream_operator(stream_classes={OutputStream}, name=name)
+
+
+__all__ = [
+    'Stream',
+]
diff --git a/requirements-base.txt b/requirements-base.txt
deleted file mode 100644
index 6afd1528..00000000
--- a/requirements-base.txt
+++ /dev/null
@@ -1,6 +0,0 @@
-future
-pytest
-pytest-mock
-pytest-runner
-sphinx
-tox
diff --git a/requirements.txt b/requirements.txt
index dfec4a10..bf565e9a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,33 +1,39 @@
-alabaster==0.7.10
-apipkg==1.4
-Babel==2.5.1
-certifi==2017.7.27.1
+alabaster==0.7.12
+atomicwrites==1.3.0
+attrs==19.1.0
+Babel==2.7.0
+certifi==2019.3.9
 chardet==3.0.4
 docutils==0.14
-execnet==1.5.0
-funcsigs==1.0.2
-future==0.16.0
-idna==2.6
-imagesize==0.7.1
-Jinja2==2.9.6
-MarkupSafe==1.0
-mock==2.0.0
-pbr==4.0.3
-pluggy==0.5.2
-py==1.4.34
-Pygments==2.2.0
-pytest==3.2.3
-pytest-forked==0.2
-pytest-mock==1.10.0
-pytest-runner==3.0
-pytest-xdist==1.22.2
-pytz==2017.3
-requests==2.18.4
-six==1.11.0
+filelock==3.0.12
+future==0.17.1
+idna==2.8
+imagesize==1.1.0
+importlib-metadata==0.17
+Jinja2==2.10.1
+MarkupSafe==1.1.1
+more-itertools==7.0.0
+packaging==19.0
+pluggy==0.12.0
+py==1.8.0
+Pygments==2.4.2
+pyparsing==2.4.0
+pytest==4.6.1
+pytest-mock==1.10.4
+pytz==2019.1
+requests==2.22.0
+six==1.12.0
 snowballstemmer==1.2.1
-Sphinx==1.6.5
-sphinxcontrib-websupport==1.0.1
-tox==2.9.1
-typing==3.6.2
-urllib3==1.22
-virtualenv==15.1.0
+Sphinx==2.1.0
+sphinxcontrib-applehelp==1.0.1
+sphinxcontrib-devhelp==1.0.1
+sphinxcontrib-htmlhelp==1.0.2
+sphinxcontrib-jsmath==1.0.1
+sphinxcontrib-qthelp==1.0.2
+sphinxcontrib-serializinghtml==1.1.3
+toml==0.10.0
+tox==3.12.1
+urllib3==1.25.3
+virtualenv==16.6.0
+wcwidth==0.1.7
+zipp==0.5.1
diff --git a/setup.py b/setup.py
index 9ec29ddc..8d54b9dc 100644
--- a/setup.py
+++ b/setup.py
@@ -69,9 +69,11 @@
     install_requires=['future'],
     extras_require={
         'dev': [
-            'future',
-            'pytest',
-            'pytest-mock',
+            'future==0.17.1',
+            'pytest-mock==1.10.4',
+            'pytest==4.6.1',
+            'Sphinx==2.1.0',
+            'tox==3.12.1',
         ],
     },
     classifiers=[