### Partial evaluation of a MV Polynomial.

I have a polynomial defined as:

q = next_prime(2^128)

P. x1, x2, x3, x4, x5 = GF(q)[]

p = (x1*x2) + (x3*x4)

I would like to obtain the resulting polynomial by partially evaluating by some variables.

Example partial polynomial p' generated by evaluating p at x2 = 2:

p' = (2*x1) + (x3*x4)

Is there a way to accomplish this?