Function include 

pub fn include<'t, I, E, F>(
    input: &'t str,
    settings: &WikitextSettings,
    includer: I,
    invalid_return: F,
) -> Result<(String, Vec<PageRef>), E>
where
    I: Includer<'t, Error = E>,
    F: FnOnce() -> E,

Replaces the include blocks in a string with the content of the pages referenced by those blocks.