How to represent the cube of variable x in CVX?

Knowing that the square of the variable x is denoted as square_pos(x), how is the cube of x denoted. And the variable x is greater than or equal to 0.

if x is a variable or affine (as opposed to a convex expression) , square_pos(x) is not needed, and x^2can be used.

Similarly, if x is a variable or affine, x^3 can be used. if x is a convex expression, pow_pos(x,3) can be used.

Note that square_pos(x) and pow_pos(x,3) are not the same as x^2 and x^3, because the output for negative arguments is zero.