sections in typedef for {use, is, has}

3.23: adda/oop/syntax/sections for use, is, has:
<use ,,,imports;
is ,,,supertypes; -- establishing type compatibility .
has ,,, subtypes;
... .
the use.section:
. why would an interface need to import a module?
they may refer to types other than self
that are not in the top-level library .
the has.section:
. a supertype has or controls its subtypes;
eg, number has all of these types:
int, real, quotient, complex, modular .