Function join_with_previous 

pub fn join_with_previous(
    root: &mut Element,
    path: &[usize],
) -> Result<Vec<usize>, Refused>

Join the paragraph at a path onto the paragraph before it among its parent’s children, and answer where the joined paragraph is.

Errors

The path leads to nothing, or the element before it is not a paragraph: there is none, or a table or a list stands between, which a join would otherwise delete.