line to curve dynamo revit
import clr
import sys
import System
clr.AddReference('ProtoGeometry')
from Autodesk.DesignScript.Geometry import *
import Autodesk.DesignScript.Geometry as DS
clr.AddReference('RevitAPI')
import Autodesk
from Autodesk.Revit.DB import *
import Autodesk.Revit.DB as DB
clr.AddReference('RevitNodes')
import Revit
clr.ImportExtensions(Revit.GeometryConversion)
clr.AddReference('RevitServices')
import RevitServices
from RevitServices.Persistence import DocumentManager
doc = DocumentManager.Instance.CurrentDBDocument
elem = UnwrapElement(IN[0])
elemsStair = [doc.GetElement(x) for x in elem.GetStairsRuns()]
stairPathCurvLoop = elemsStair[0].GetStairsPath()
OUT = [x.ToProtoType() for x in stairPathCurvLoop]