get the coefficients from the Polynomial

edit

Just like that

R.<x> = GF(2^4, 'a')[]

f=x^3+x+1

print f.coefficients()

it returns [1, 1, 1],but I want it to retun [1,0,1,1],that is i need all the coefficients of every term（x^3,x^2,x^1,x^0）,what should i do? thanks