如何在beam中访问combine.perKey中的key

import apache_beam as beam

class MyDoFn(beam.DoFn):
    def process(self, element):
        key, values = element
        # 在这里可以访问combine.perKey中的key
        print("Key:", key)
        for value in values:
            # 处理每个key对应的value
            print("Value:", value)

# 创建一个Pipeline
pipeline = beam.Pipeline()

# 从某个数据源读取数据
data = pipeline | beam.Create([('A', 1), ('B', 2), ('A', 3), ('B', 4)])

# 使用combine.perKey对数据进行聚合
result = data | beam.CombinePerKey(sum)

# 应用自定义的DoFn函数来处理结果
result | beam.ParDo(MyDoFn())

# 运行Pipeline
pipeline.run()