/**
* refer
* - /models/datatype.js; constraint_filters
* - /models/patterns.js; type_constraint_parse, type_constraint_serialize
**/
// which are inherits the type
- `/` inherits: datatype
// which contains the type in its items property
- `@` contains: datatype
// exact the type
- `!` datatype
// has keyname (~is not a datatype) in its items property
- `#` keyname
run type constraints/hints such as: