List of variables : lname indets

lname (or indets) takes as argument an expression.
lname (or indets) returns the list of the symbolic variable names used in this expression.
Input :

lname(x*y*sin(x))

Output :

[x,y]

Input :

a:=2;assume(b>0);assume(c=3);

lname(a*x^2+b*x+c)

Output :

[x,b,c]