How to programmatically erase a date column cell, with project settings and dependencies enabled?

gistfile1.txt

import smartsheet

def remove_start_date(sheet_id, row_number):   
    access_token = "" # your access token
    smartsheet_client = smartsheet.Smartsheet(access_token)
    sheet = smartsheet_client.Sheets.get_sheet(sheet_id)

    # Create Column Map
    column_map = {}
    for column in sheet.columns:
        column_map[column.title] = column.id

    row_id = sheet.rows[row_number].id
    column_id = column_map['Start']

    # Build the row to update
    new_row = smartsheet.models.Row()
    new_row.id = row_id

    # Remove Predecessors
    new_cell = smartsheet.models.Cell()
    new_cell.column_id = column_map["Predecessors"]
    new_cell.value = ""
    new_cell.strict = False
    new_row.cells.append(new_cell)

    # Remove Start Date Value
    new_cell = smartsheet.models.Cell()
    new_cell.column_id = column_map['Start']
    new_cell.value = "None"  # "" or "  " does not work so "nothing" etc.
    new_cell.strict = False
    new_row.cells.append(new_cell)

    # Update rows
    updated_row = smartsheet_client.Sheets.update_rows(
        sheet_id,      # sheet_id
        [new_row]
    )

if __name__ == '__main__':
    sheet_id = input('sheet_id')
    row_number = int(input('row number'))
    remove_start_date(sheet_id, row_number)