### How do I define (and work with) a set of matrices?

Suppose $a,b,c$
are matrices, and I want to define the set ~~$S=${$a,b,c$}$.
~~$S=$ { $a,b,c$ }.
What is the proper syntax for this? More generally, how do I define a set by specifying its elements (regardless of their nature). I am only finding documentation for sets of numbers.

I'm also interested in doing functions that take sets like $S$
as input.
For instance, if I had a matrix $d$,
I want to be able to define a set like ~~$S'=${$da,db,dc$}$,
~~$S'=$ { $da,db,dc$},
but I want to be able to do this via the Sage equivalent of $f(S):={ms\mid s\in S}$.