Beam SlidingWindows是Apache Beam中的一个实用程序函数，用于在一个PCollection中生成重叠的窗口。在使用此函数时，发现元素没有按预期方式复制到多个窗口中。

出现这个问题的原因是，Beam SlidingWindows使用Python中的itertools中的函数tee()来生成重叠窗口，但是tee()函数不是“安全”函数，可能会生成重复元素。

为了解决这个问题，我们可以使用另一个itertools中的函数zip()替代tee()。zip()函数可以安全地迭代两个或多个可迭代对象，并将其元素组合到一个元组中。这可以确保不会复制元素。

以下是使用zip()函数解决问题的代码示例：

from itertools import zip_longest

class CustomSlidingWindows(object):

def __init__(self, size=2, offset=1):
    self.size = size
    self.offset = offset

def __eq__(self, other):
    return isinstance(other, CustomSlidingWindows) and \
           self.size == other.size and \
           self.offset == other.offset

def __repr__(self):
    return 'CustomSlidingWindows(size={}, offset={})'.format(self.size, self.offset)

def __str__(self):
    return '{}/{}'.format(self.size, self.offset)

def assign(self, element):
    start = element[0] - self.size
    stop = element[0] + self.offset
    return [(start, stop)]

def merge(self, intervals):
    return [(min(x[0] for x in intervals), max(x[1] for x in intervals))]

def expand(self, window):
    # We expand the window to support back-filling previous elements.
    # Also in case of overlapping windows, it might already contain elements from the previous window.
    start = window[0] - self.offset
    stop = window[1]
    return [(start, stop)]

def split(self, window):
    idx = int(((window[1] - window[0]) / self.size) / 2)
    if idx == 0:
        return [window]
    else:
        intervals = []
        for i in range(idx):
            intervals.append((window[0] + (i * self.offset), window[0] + self.size + (i * self.offset)))
        if (idx * self.offset) < (window[1] - window[0]):
            intervals.append((window[0] + (idx * self.offset), window[1]))
        return intervals

def get_window_start(self, window):
    return window[0]

def get_window_size(self, window):
    return window[1] - window[0]

def get_window_coder(self):
    return IntervalWindowCoder()

def get_transform(self):
    return SlidingWindows(self.size, self.offset)

def get_suggested_key(self):
    return KeyParam()

def get_param_names(self):
    return ["size", "offset"]

def get_defaults(self):
    return ["2", "1"]

def run(): with beam.Pipeline() as p: ranges = p | "create" >> beam.Create([ (1, "a"), (2, "b"), (5, "c"), (6, "d"), (7, "e") ])

    results = ranges | "ranges" >> beam.WindowInto(
        CustomSlidingWindows(size=2, offset=1),