Function intersect_periods 

pub fn intersect_periods<T: TimeInstant>(
    a: &[Interval<T>],
    b: &[Interval<T>],
) -> Vec<Interval<T>>

Returns the intersection of two sorted, non-overlapping period lists.

Uses an O(n+m) merge algorithm to find all overlapping spans.

Arguments

• a - First sorted, non-overlapping period list
• b - Second sorted, non-overlapping period list

Returns

Periods where both a and b overlap, in chronological order.