Function apply_bulk_insertions 

pub fn apply_bulk_insertions<T, I>(target: &mut Vec<T>, insertions: I)
where
    I: Iterator<Item = Insertion<T>> + ExactSizeIterator,

Applies all the specified insertions into the target vector.

The insertion iterator must be sorted in reverse order and give the proper size for its ExactSizeIterator. Violating these constraints will never cause undefined behavior, since internally we use the completely safe BulkShifter abstraction.