title: Shape numbers/indexes of each pptx slide within existing presentation
body: <p>I am new to python pptx library and my question is: How can I define the list of shapes, the shape numbers/indexes (shapetree) and shape types of each pptx slide within an existing presentation using Python Library pptx? I would like to update an existing ppt presentation and it seems that the first step would be to locate exact shape identifiers on each slide to access them with the updates.  Would you point me to an existing solution or possibly examples? </p>