The valve checker

A list gives the pressures in an atrium, a ventricle and an artery, in mm Hg, at several moments. You will decide which valve is open at each moment.

The idea. A valve opens when the pressure behind it is higher than the pressure in front of it.

Your tasks.

1. Finish av_open. It gives True when the valve between the atrium and the ventricle is open.
2. Finish phase. It gives "filling" when that valve is open, "pumping" when the valve between the ventricle and the artery is open, and "both shut" otherwise.
3. Set pumping to the number of moments in the list when the heart is pumping.