defs element is used to store graphical objects that will be used at a later time. Objects created inside a
defs element are not rendered directly. To display them you have to reference them (with a
use element for example).
Usually, this element is create with:
const defs = parentElement.add('defs')
It's possible create as a disconnected element with
gySVG('defs') and attach it to the SVG document with
Child elements: a | animate | animateMotion | animateTransform | circle | clipPath | defs | desc | discard | ellipse | filter | foreignObject | g | image | line | linearGradient | marker | mask | metadata | mpath | path | pattern | polygon | polyline | radialGradient | rect | set | stop | style | svg | switch | symbol | text | title | use | view.