In the Agile world, ScrumMaster and Agile Coaches are often referred to as a gardener that helps a seed grow to provide shade and/or a fruitful tree. You need to prepare the ground, remove weed and give enough nutrition for good growth. At workplace, this resembles creating a safe environment for a person to do the work.
After getting inspiration from High-Performance Tree metaphor, I thought about why not create a retrospective model from it. You can use this retrospective model for Sprint or any other project closure as well.