address sabet's comments

baseclasses/solvers/pyAero_solver.py

@@ -80,7 +80,7 @@ def setMesh(self, mesh):
         pts = self.getSurfaceCoordinates(self.meshFamilyGroup)
         self.mesh.setSurfaceDefinition(pts, conn, faceSizes)
 
-    def setDVGeo(self, DVGeo, pointSetKwargs={}, customPointSetFamilies=None):
+    def setDVGeo(self, DVGeo, pointSetKwargs=None, customPointSetFamilies=None):
         """
         Set the DVGeometry object that will manipulate 'geometry' in
         this object. Note that <SOLVER> does not **strictly** need a
@@ -98,8 +98,12 @@ def setDVGeo(self, DVGeo, pointSetKwargs={}, customPointSetFamilies=None):
             These arguments are used for all point sets added by this solver.
 
         customPointSetFamilies : dict of dicts
-            Keyword arguments to be passed to the DVGeo addPointSet call for each surface family,
-            specified by the keys. The surface families need to be all part of the designSurfaceFamily.
+            This argument is used to split up the surface points added to the DVGeo by the solver into potentially
+            multiple subsets. The keys of the dictionary will be used to determine what families should be
+            added to the dvgeo object as separate point sets. The values of each key is another dictionary, which can be empty.
+            If desired, the inner dictionaries can contain custom kwargs for the addPointSet call for each surface family,
+            specified by the keys of the top level dictionary.
+            The surface families need to be all part of the designSurfaceFamily.
             Useful for DVGeometryMulti, specifying FFD projection tolerances, etc.
             If this is provided together with pointSetKwargs, the regular pointSetKwargs
             will be appended to each component's dictionary. If the same argument
@@ -115,10 +119,16 @@ def setDVGeo(self, DVGeo, pointSetKwargs={}, customPointSetFamilies=None):
         self.DVGeo = DVGeo
 
         # save the common kwargs dict. default is empty
-        self.pointSetKwargs = pointSetKwargs
+        if pointSetKwargs is None:
+            self.pointSetKwargs = {}
+        else:
+            self.pointSetKwargs = pointSetKwargs
 
         # save if we have customPointSetFamilies
-        self.customPointSetFamilies = customPointSetFamilies
+        if customPointSetFamilies is None:
+            self.customPointSetFamilies = None
+        else:
+            self.customPointSetFamilies = customPointSetFamilies
 
     def getTriangulatedMeshSurface(self, groupName=None, **kwargs):
         """