PathObject contains the SVG elements in the DOM
that make up the block.
For example, in the Geras renderer, blocks have a "main" path, a "dark" path and a "light" path, to give them a 3d effect. The path object creates the SVG elements for each of these paths.
This is opposed to the Thrasos renderer, whose blocks have a single path element with a stroke:
It also handles: