使用给定的fn将所有元素规约为单个元素, 等同于 :func:`bigflow.transforms.reduce(self, fn, *side_inputs, **options) `, Args: fn (function): 规约函数 *side_inputs: 参与运算的SideInputs **options: 可配置参数 Returns: P
(self, fn, *side_inputs, **options)
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no outgoing calls