The projective-space exceptional-locus conjecture for symplectic contractions

Let $X$ be a smooth projective symplectic variety of dimension $2n$, and let

$$X\longrightarrow Z$$

be a birational contraction whose degenerate locus $B$ is contracted to isolated points. Projective-space exceptional-locus conjecture. The locus $B$ is a disjoint union of smooth subvarieties, each isomorphic to ${\Bbb P}^n$. The result is known when a smooth subvariety is contracted to a point, but the stated assertion for an entire degenerate locus is presented as an expectation and remains open.