diff --git a/examples/kitchen_sink.py b/examples/kitchen_sink.py
index c1bd730..eba5e62 100644
--- a/examples/kitchen_sink.py
+++ b/examples/kitchen_sink.py
@@ -1,4 +1,17 @@
-from pyxdsm.XDSM import XDSM, OPT, SUBOPT, SOLVER, DOE, IFUNC, FUNC, GROUP, IGROUP, METAMODEL
+from pyxdsm.XDSM import (
+    XDSM,
+    OPT,
+    SUBOPT,
+    SOLVER,
+    DOE,
+    IFUNC,
+    FUNC,
+    GROUP,
+    IGROUP,
+    METAMODEL,
+    LEFT,
+    RIGHT,
+)
 
 x = XDSM()
 
@@ -22,7 +35,10 @@
 # stacked can be used to represent multiple instances that can be run in parallel
 x.add_system("H", FUNC, "H", stack=True)
 
-x.add_process(["opt", "DOE", "MDA", "D1", "D2", "subopt", "G1", "G2", "MM", "F", "H", "opt"], arrow=True)
+x.add_process(
+    ["opt", "DOE", "MDA", "D1", "D2", "subopt", "G1", "G2", "MM", "F", "H", "opt"],
+    arrow=True,
+)
 
 x.connect("opt", "D1", ["x", "z", "y_2"], label_width=2)
 x.connect("opt", "D2", ["z", "y_1"])
@@ -50,12 +66,12 @@
 x.add_input("opt", r"x_0", stack=True)
 
 # can put outputs on the left or right sides
-x.add_output("opt", r"x^*, z^*", side="right")
-x.add_output("D1", r"y_1^*", side="left")
-x.add_output("D2", r"y_2^*", side="left")
-x.add_output("F", r"f^*", side="right")
-x.add_output("H", r"h^*", side="right")
-x.add_output("opt", r"y^*", side="left")
+x.add_output("opt", r"x^*, z^*", side=RIGHT)
+x.add_output("D1", r"y_1^*", side=LEFT)
+x.add_output("D2", r"y_2^*", side=LEFT)
+x.add_output("F", r"f^*", side=RIGHT)
+x.add_output("H", r"h^*", side=RIGHT)
+x.add_output("opt", r"y^*", side=LEFT)
 
 x.add_process(["output_opt", "opt", "left_output_opt"])
 
diff --git a/examples/mdf.py b/examples/mdf.py
index 4817f3d..65c89f1 100644
--- a/examples/mdf.py
+++ b/examples/mdf.py
@@ -1,4 +1,4 @@
-from pyxdsm.XDSM import XDSM, OPT, SOLVER, FUNC
+from pyxdsm.XDSM import XDSM, OPT, SOLVER, FUNC, LEFT
 
 # Change `use_sfmath` to False to use computer modern
 x = XDSM(use_sfmath=True)
@@ -23,9 +23,9 @@
 x.connect("F", "opt", "f")
 x.connect("G", "opt", "g")
 
-x.add_output("opt", "x^*, z^*", side="left")
-x.add_output("D1", "y_1^*", side="left")
-x.add_output("D2", "y_2^*", side="left")
-x.add_output("F", "f^*", side="left")
-x.add_output("G", "g^*", side="left")
+x.add_output("opt", "x^*, z^*", side=LEFT)
+x.add_output("D1", "y_1^*", side=LEFT)
+x.add_output("D2", "y_2^*", side=LEFT)
+x.add_output("F", "f^*", side=LEFT)
+x.add_output("G", "g^*", side=LEFT)
 x.write("mdf")
diff --git a/pyxdsm/XDSM.py b/pyxdsm/XDSM.py
index 7949bda..392cd66 100644
--- a/pyxdsm/XDSM.py
+++ b/pyxdsm/XDSM.py
@@ -16,6 +16,8 @@
 GROUP = "Group"
 IGROUP = "ImplicitGroup"
 METAMODEL = "Metamodel"
+LEFT = "left"
+RIGHT = "right"
 
 tikzpicture_template = r"""
 %%% Preamble Requirements %%%
@@ -126,7 +128,16 @@ def __init__(self, use_sfmath=True):
 
         self.use_sfmath = use_sfmath
 
-    def add_system(self, node_name, style, label, stack=False, faded=False, label_width=None, spec_name=None):
+    def add_system(
+        self,
+        node_name,
+        style,
+        label,
+        stack=False,
+        faded=False,
+        label_width=None,
+        spec_name=None,
+    ):
         """
         Add a "system" block, which will be placed on the diagonal of the XDSM diagram.
 
@@ -237,9 +248,18 @@ def add_output(self, name, label, label_width=None, style="DataIO", stack=False,
         elif side == "right":
             self.right_outs[name] = Output("right_output_" + name, label, label_width, style, stack, side)
         else:
-            raise ValueError("The option 'side' must be given as either 'left' or 'right!'")
-
-    def connect(self, src, target, label, label_width=None, style="DataInter", stack=False, faded=False):
+            raise ValueError("The option 'side' must be given as either 'left' or 'right'!")
+
+    def connect(
+        self,
+        src,
+        target,
+        label,
+        label_width=None,
+        style="DataInter",
+        stack=False,
+        faded=False,
+    ):
         """
         Connects two components with a data line, and adds a label to indicate
         the data being transferred.
diff --git a/pyxdsm/__init__.py b/pyxdsm/__init__.py
index 8a124bf..b19ee4b 100644
--- a/pyxdsm/__init__.py
+++ b/pyxdsm/__init__.py
@@ -1 +1 @@
-__version__ = "2.2.0"
+__version__ = "2.2.1"
diff --git a/tests/test_xdsm.py b/tests/test_xdsm.py
index cc18fc9..6515712 100644
--- a/tests/test_xdsm.py
+++ b/tests/test_xdsm.py
@@ -3,7 +3,7 @@
 import shutil
 import tempfile
 import subprocess
-from pyxdsm.XDSM import XDSM, OPT, FUNC, SOLVER
+from pyxdsm.XDSM import XDSM, OPT, FUNC, SOLVER, LEFT, RIGHT
 from numpy.distutils.exec_command import find_executable
 
 basedir = os.path.dirname(os.path.abspath(__file__))
@@ -92,10 +92,10 @@ def test_options(self):
         x.connect("F", "opt", "f")
         x.connect("G", "opt", "g")
 
-        x.add_output("opt", "x^*, z^*", side="right")
-        x.add_output("D1", "y_1^*", side="left", stack=True)
-        x.add_output("D2", "y_2^*", side="left")
-        x.add_output("F", "f^*", side="left")
+        x.add_output("opt", "x^*, z^*", side=RIGHT)
+        x.add_output("D1", "y_1^*", side=LEFT, stack=True)
+        x.add_output("D2", "y_2^*", side=LEFT)
+        x.add_output("F", "f^*", side=LEFT)
         x.add_output("G", "g^*")
         x.write(filename)
         x.write_sys_specs(spec_dir)