等同于 :func:`bigflow.transforms.accumulate(self, zero, accumulate_fn, *side_inputs, **options) ` Args: zero (value or function): 初始值,或是一个返回初始值的方法 accumulate_fn (function): 聚合方法 *side_inputs: 参与运算的SideInpu
(self, zero, accumulate_fn, *side_inputs, **options)
source not stored for this graph (policy: none)
no outgoing calls