Hello
the method ScheduleField.ResetOverride() is not suitable for this.
it is necessary to apply an empty TableCellStyle object with method SetCellStyle()
import clr
clr.AddReference('ProtoGeometry')
from Autodesk.DesignScript.Geometry import *
#import Revit API
clr.AddReference('RevitAPI')
import Autodesk
from Autodesk.Revit.DB import *
clr.AddReference('RevitServices')
import RevitServices
from RevitServices.Persistence import DocumentManager
from RevitServices.Transactions import TransactionManager
doc = DocumentManager.Instance.CurrentDBDocument
toList = lambda x : x if hasattr(x, "__iter__") else [ x ]
viewsSchedule = toList(UnwrapElement(IN[0]))
tableStyle = TableCellStyle()
tableStyle.ResetOverride() #optional
TransactionManager.Instance.EnsureInTransaction(doc)
for view in viewsSchedule:
if view.ViewType == ViewType.Schedule:
tableData = view.GetTableData()
headerSect = tableData.GetSectionData(SectionType.Header)
headerSect.SetCellStyle(tableStyle)
TransactionManager.Instance.TransactionTaskDone()
OUT = viewsSchedule