如何在openpyxl中排除条件格式中的空白单元格？

from openpyxl import Workbook
from openpyxl.styles import PatternFill
from openpyxl.styles.differential import DifferentialStyle
from openpyxl.formatting.rule import Rule
from openpyxl.utils import get_column_letter

# 创建一个新的工作簿
wb = Workbook()
ws = wb.active

# 填充一些数据
data = [
    ['Name', 'Score'],
    ['Alice', 85],
    ['Bob', None],
    ['Charlie', 90],
    ['Dave', None],
    ['Eve', 95]
]

for row in data:
    ws.append(row)

# 创建一个条件格式规则，仅在单元格不为空时应用
fill = PatternFill(start_color="FFFF00", end_color="FFFF00", fill_type="solid")
diff_style = DifferentialStyle(fill=fill)
rule = Rule(type="expression", dxf=diff_style)
rule.formula = 'NOT(ISBLANK($B1))'
ws.conditional_formatting.add('B2:B7', rule)

# 保存工作簿
wb.save('example.xlsx')