如何使用Apache光束最新转换从pcoll获取最新的时间戳？

import apache_beam as beam
from apache_beam.transforms.trigger import AfterWatermark, AfterProcessingTime, AccumulationMode
from apache_beam.transforms.trigger import AfterCount, Repeatedly, AfterAny

pipeline = beam.Pipeline()

class ExtractTimestampFn(beam.DoFn):
    def process(self, element):
        # 在这里根据数据结构提取时间戳
        timestamp = element['timestamp']
        yield beam.window.TimestampedValue(element, timestamp)

class MyTransform(beam.PTransform):
    def expand(self, pcoll):
        return (
            pcoll
            | '提取时间戳' >> beam.ParDo(ExtractTimestampFn())
            | '其他转换操作' >> beam.Map(...)
        )

pcoll = pipeline | '读取数据' >> beam.io.ReadFrom...
result = pcoll | '应用转换函数' >> MyTransform() | '设置触发器' >> beam.WindowInto(
    beam.window.FixedWindows(10),
    trigger=AfterWatermark(early=AfterProcessingTime(5), late=AfterCount(3)),
    accumulation_mode=AccumulationMode.DISCARDING
)