pub fn remove(&mut self, addr: u32) -> Option<V> {
        let (upper, lower) = Self::indices(addr);
        let index = self.index[upper];
        if index == NO_PAGE {
            None
        } else {
            self.page_table[index as usize].0[lower].take()
        }
    }
Remove the value at the given address if it exists, returning it.
crates/core/executor/src/memory.rs