Create Generation matrix from Function to check CCZ

Question

Here is an example of checking CCZ-equivalence. How to rewrite the following function CF from Magma to GAP-system?

p=2;n=6;
function CF(f)
    M:=Matrix(  2*n+1, p^n,  
               [1: x in GF]    
         cat   [Trace(a^i * x): x in GF, i in [1..n]]   
         cat   [Trace(a^i * f(x)): x in GF, i in [1..n]]);
    return LinearCode( M );
end function;
f1:=func<x | x^3 >;
CF(f1);