Ahlfors extremals realizing the gonality

Let a compact bordered Riemann surface have gonality equal to the least degree of a conformal map to the disc, and let $f_{a,b}$ denote an Ahlfors extremal function associated with two marked points, with $f_a$ the limiting one-point extremal. Ahlfors gonality conjecture. Any conformal mapping realizing the gonality arises as an Ahlfors extremal function $f_{a,b}$, perhaps after coalescing two points to obtain an Ahlfors map $f_a$ maximizing the modulus of the derivative at $a$. The source records the question as unsettled; it is proved there only in the hyperelliptic case.