Sometimes when a problem seems like it's nothing you've ever seen before, you can really start to feel like an impostor.
But, while it's always a good idea to make sure that you're not overlooking something basic, like a tool for the job that you just haven't heard about, it sometimes really means that it's a novel problem, one that doesn't have a tool yet.
So, sometimes you're not being an impostor, you're breaking new ground. And sometimes, the way you "fake it" is really the best new way to do it.

So, do your homework, but don't be afraid to have a go, either.