Is this Japanese knotweed?

I noticed this weed sprouting up in the beds in my front garden, and I’m not sure if it’s Japanese knotweed.

I’m thinking it’s not because it’s not growing in the typical zig-zag, but the bases of some leaves look kind of flat. Anyone with more experience that could help?

It grows on long vines, and has really taken off over the last month. I’d get someone in to look at it, but it’s actually growing in from the neighbours property so I want to be sure before I bother them about it.