Base space of Lagrangian fibrations of symplectic varieties

I will talk about a base space of Lagrangian fibrations of symplectic varieties. Hwang proved that the base space of a Lagrangian fibration of an irreducible symplectic manifold is the projective space if the base space is smooth. I will give an alternative proof of this result which can be applied a Lagrangian fibration which defined on singular symplectic variety.