Method cumsum

ot/backend.py:2031–2035

(self, a, axis=None)

            return torch.sum(a, axis, keepdim=keepdims)

    def cumsum(self, a, axis=None):
        if axis is None:
            return torch.cumsum(a.flatten(), 0)
        else:
            return torch.cumsum(a, axis)

    def max(self, a, axis=None, keepdims=False):
        if axis is None: