structure assertions demo

Now we see actual two more or less similar implementations of a material design card, as we found it described in the mdl documentation. In the first and either the second card, we placed some errors, that should give you a hint about what structure-assertions can do for you.

And yes, that is only a brief example with no really sense. But see just try to see structure-assertions as a tool, that users may use to understand your componens and keep their usage compliant to it.