> - with transformations between them
    >
    > - including a ‘do nothing’ transformation
    >
    > - that can be composed associatively (a sequence of statements `{a; b;}; c` transforms the state in the same way as a sequence of statements `a; {b; c;}`)

And this right here is that monoid in the famous "A monad is just a monoid in the category of endofunctors" meme.