Description
To get the design option of a set of elements (for filtering purposes) you first need to check if the design option is set or not and then access it. For most elements in Dynamo you first need to get the DB element and then access the required property.

Solution
import clr
clr.AddReference("RevitAPI");
from Autodesk.Revit.DB import *
clr.AddReference("RevitServices")
from RevitServices.Persistence import DocumentManager
doc = DocumentManager.Instance.CurrentDBDocument
def getDesignOptionName(element):
el = doc.GetElement(ElementId(element.Id))
if el.DesignOption <> None:
return el.DesignOption.Name
return ""
ret = []
for each in IN[0]:
ret.append(getDesignOptionName(each))
#Assign your output to the OUT variable.
OUT = ret









